Factor Xiii Medscape

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Practice Essentials

Factor XIII (FXIII), which was initially termed fibrin stabilizing factor, is involved in clot

preservation. FXIII deficiency, an autosomal recessive disorder, is a rare but potentially life-threatening cause of a hemorrhagic diathesis. Paradoxically, alterations in FXIII may also

predispose to thrombosis. FXIII participates in other physiologic processes, including woundrepair and healing.

Essential update: FDA approves recombinant product for prophylaxis in factor

XIII deficiency

In December 2013, the FDA approved recombinant coagulation factor XIII A-subunit (Tretten)for the prevention of bleeding in adults and children with congenital factor XIII A-subunit

deficiency. Approval was based on studies in 77 patients in which monthly treatment with the

coagulation factor effectively prevented bleeding in 90% of subjects.[1]

Signs and symptoms

The following symptoms should trigger an evaluation for FXIII deficiency:

Spontaneous miscarriages early in pregnancy

Bleeding from the umbilical cord 1-19 days after birth

Easy bruising and soft tissue bleeding, particularly in association with trauma, as the

infant starts to ambulate; bleeding following trauma may be immediate, delayed, and/or

recurrent

CNS hemorrhage is common, recurs in approximately 30% of patients, and may be the

initial manifestation in patients with severe FXIII deficiency

CNS bleeding may be preceded by head trauma in children, while adults may develop a

CNS bleed in the absence of obvious trauma

Symptoms typical of any CNS event may be present (eg, headaches, seizures, vomiting,

focal neurologic defects); symptoms may be acute at onset or may be superimposed on

residual findings of a past bleed

Menorrhagia and intra-abdominal bleeding during menses

Bleeding into joints

Poor wound healing, although described, is less common

Autoantibodies to FXIII are an acquired cause of a bleeding diathesis; these may be

triggered by isoniazid, so a detailed drug history is essential

Bleeding into joints

May be precipitated by trauma

Reports exist of recurrent target joint bleeds, but destructive changes in the joints are

uncommon[2]

Spontaneous joint and extensive muscle bleeding, characteristic of patients with severehemophilia, are uncommon in patients with severe FXIII deficiency


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Physical findings

Physical findings depend on the site at which bleeding develops and include the following:

Bleeding from the umbilical cord after birth usually manifests with persistent oozing,

which may start a few days after birth Findings associated with CNS bleeding depend on the location of the bleeding; trauma

may precede the event, with additional findings, a new CNS bleed may be superimposed

on residual findings related to a prior bleed

Findings in patients with bruising and soft tissue bleeding are similar to those seen in

other patients; it is uncommon to find the large hematomas or joint bleeds characteristic

in patients with severe hemophilia

Female patients may present with vaginal spotting or bleeding during early pregnancy,

preceding a spontaneous miscarriage

Persistent, delayed, or recurrent bleeding may occur at sites of trauma or surgery

Poor wound healing may be noted

Acquired causes of FXIII deficiency, such as DIC and liver disease, present in a well-recognized manner

SeeClinical Presentationfor more detail.

Diagnosis

The following routine tests are the first step in the evaluation of any bleeding disorder:

aPTT

PT

Thrombin Clottable fibrinogen level

Platelet count

Bleeding time (after ascertaining that the patient was not on antiplatelet drugs for at least

the preceding 5 d)

However, these tests cannot be used to screen for FXIII deficiency because the results would bewithin reference ranges in a patient with isolated severe FXIII deficiency.

[3]

Qualitative screening test for severe FXIII deficiency

Assessment of clot solubility in 5M urea or 1% monochloroacetic acid Lysis of thrombin and Ca2+ - induced clot within a few hours suggests severe FXIII

deficiency, provided that fibrinogen levels are qualitatively and quantitatively within

reference range

The thrombin-clottable fibrinogen test can be used to exclude hypofibrinogenemia and

dysfibrinogenemia, which cause false-positive results on the 5M urea solubility test

Quantitive testing
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If the 5M urea solubility test demonstrates positive results, this finding should be confirmed by

quantitating FXIII activity using a monodansylcadaverine or putrescine incorporation assay.

A new sensitive assay used to quantitate FXIII activity is based on monitoring the amount of

ammonia (NH3) released by using glutamate dehydrogenase and nicotinamide adenine

dinucleotide phosphate during the transamidation reaction (cross-linking) by FXIII. Another newand sensitive colorimetric assay is based on incorporation of 5-(biotinamido) pentylamine into

fibrin/fibrinogen.[4]

In addition, a2PI and plasminogen activator inhibitor-1 assays should be performed to exclude

abnormalities in the fibrinolytic pathway, which accelerate clot lysis. Sodium dodecylsulfate

polyacrylamide gel electrophoresis under reducing conditions has been used to assess thepresence of cross-linked g or a chains of fibrin, which is a reflection of FXIII activity. The

studies must be performed by laboratory personnel with special expertise.

Testing for inhibitors

Repeat the urea solubility test with mixtures containing varying proportions of patientand normal plasma to differentiate between a deficiency or an inhibitor as the cause of a

positive result; serum may be substituted for plasma in the test

Semiquantitation of the susceptibility of the fibrin clot to fibrinolysis can be obtained byadding iodine-125-labeled fibrinogen, tissue plasminogen activator, thrombin, and Ca

2+

to the patient's plasma, with measurement of the time to 50% clot lysis

Prenatal diagnosis

Chorionic villous sampling at approximately 10-12 weeks of gestation or amniocentesis

at 16-20 weeks of gestation can be performed to obtain fetal cells for DNA analysis or forlinkage studies

If DNA analysis cannot be performed, fetal blood obtained by fetoscopy at approximately20 weeks of gestation can be used

Perform these procedures only after intense genetic and obstetric counseling of the

parents

SeeWorkupfor more detail.

Management

FXIII replacement is used to treat bleeding, to prevent perioperative bleeding during electivesurgical procedures or, prophylactically, to prevent recurrent bleeding, as in CNS or jointhemorrhages. Serial monitoring of achieved FXIII levels is essential to document the adequacy

of any therapy.

FXIII concentrates for replacement are as follows:
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Plasma-derived virus-inactivated human FXIII concentrate (Corifact, in the United

States; Fibrogammin P in Europe, South America, South Africa, and Japan); a second

FXIII concentrate (Bio Products Laboratory, Elstree, Hertfordshire, UK) is available on aper-patient request

Recombinant FXIII A-subunit, recombinant (Tretten)

Minor bleeding, as from cuts and abrasions, may respond to conservative measures, such as

pressure, ice, and use of antifibrinolytic drugs. Avoidance of trauma and nonsteroidal anti-

inflammatory drugs (NSAIDs) is helpful in reducing bleeding events.

Treatment of patients with inhibitors

FXIII dose depends on the characteristics of the inhibitor

Also treat the underlying disorder and, when appropriate, use immunosuppressive agents,

including the newer B-cell-directed monoclonal antibodies.

Note that spontaneous disappearance of acquired inhibitors is part of their natural history,

and the use of milder less toxic immunomodulators, such as steroids, may suffice Simple immediate ancillary measures of ice, pressure, ace wrap, immobilization of the

affected joint, and avoidance of NSAIDs may suffice in some cases

SeeTreatmentandMedicationfor more detail.

Image library

Coagulation reactions leading to thrombin generation andactivation of factor XIII.

Background

The hemostatic system, consisting of blood vessels and blood, plays a crucial role in human

survival. The importance of the plasma coagulation system in protecting life and preventing

further blood loss following transection of a blood vessel has been understood for a long time.Blood normally is maintained in a fluid state, without evidence of bleeding or clotting. The

presence of a bleeding diathesis in families with an X-linked pattern of inheritance of the

disorder has been recognized for hundreds of years.

The recognition of factor deficiencies as the cause of hemophilias spurred investigations into the

causes of other bleeding disorders and led to progress in understanding normal hemostasis.Knowledge of the fact that blood clots that are formed in the presence of calcium are stronger,

insoluble in alkali, and resistant to proteolytic degradation led to the concept of insoluble clots in
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the earlier part of the last century. In 1948, Laki and Lorand recognized that a serum factor,

termed fibrin stabilizing factor, was responsible for the characteristics of insoluble fibrin clots.[5]

In 1960, Duckert et al described the first case of an "undescribed congenital haemorrhagicdiathesis probably due to fibrin stabilizing factor deficiency," which was a description of the

consequences of severe factor XIII (FXIII) deficiency.[6, 7]

The importance of FXIII in the process of coagulation is underscored by symptoms borne by

patients who are homozygously deficient in FXIII or who have an antibody that disrupts FXIII

function. Paradoxically, alterations in FXIII may predispose patients to thrombosis. Based on allavailable data, FXIII is clearly involved in the clot preservation side of the delicate balance

between clot formation and stability and clot degradation. FXIII participates in other physiologic

processes, including wound repair and healing. The many functions of FXIII and the disruptions

of those functions by mutations in the genes coding for FXIII are the subjects of on-goinginvestigations.

[8, 9, 10]

Gene polymorphisms are being evaluated for their influence on susceptibility to venous and

arterial thromboembolism.

[11]

Variants of coagulation factors, including factor XIII Val34Leu,have been implicated in influencing susceptibility to thromboembolic diseases.[12]

There is a question as to whether factor XIII Val34Leu polymorphism is protective against

idiopathic venous thromboembolism.[13]

The substitution of leucine for valine at amino acid

position 34 of the factor XIII gene, commonly referred to as FXIII Val34Leu polymorphism, hasbeen reported to confer protection against venous thromboembolism. However, the results of a

recent study of white Canadian study population do not support an independent association of the

FXIII Val34Leu polymorphism with idiopathic venous thromboembolism.

An association may exist between the factor XIII Leu allele and a modest protective effect

against AMI and may provide useful information in profiling susceptibility to myocardialinfarction.[14]

Factor XIII has a variety of uses, potential and real. Plasma levels of factor XIII were founddecreased in children with HenochSchnlein purpura having severe abdominal symptoms.

Thus, it has been suggested that measurement of factor XIII level may be of value to detect the

vasculitic process of HenochSchnlein purpura before the rash occurs or long after it hasdisappeared in patients with isolated abdominal or scrotal problems.

[15, 16]

Immunohistochemistry may show factor XIIIa (FXIIIa).[17]

FXIIIa-positive dermal dendritic cells

were increased in a variety of skin tumors, including dermatofibromas.

Severe factor XIII deficiency, a rare autosomal recessive coagulation disorder, is associated with

a relatively common prevalence ofF13Bgene defects, at least within the German population.The regions in and around the cysteine disulphide bonds in the FXIII-B protein at the sites of

frequent mutations.[18]

FXIIIs aids immobilization and killing of bacteria as well as phagocytosis by macrophages,

likely functioning as part of the innate immune system.[19]


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Use of relatively new specific FXIII assays are pivotal to avoid missing the diagnosis of FXIII

deficiency, a rare but potentially life-threatening disorder.[20]

Pathophysiology

Structure, production, and half-life of FXIII

Plasma FXIII is a heterotetramer consisting of 2 identical proenzyme subunits (A2) and 2

identical carrier protein subunits (B2). Subunit A contains the catalytic site, the activation

peptide, a calcium-binding site, and free sulfhydryl (SH) groups. Subunit B, a glycoprotein, actsas a carrier protein that stabilizes subunit A, binds the zymogen (subunit A) to fibrinogen, and

acts as a brake on FXIII activation.[21, 22]

Subunit B circulates in plasma as part of the tetramer A2

B2and as a free B2dimer; all of plasma subunit A is complexed with subunit B. The

concentration of subunit A in plasma is 15 mg/mL, while that of subunit B is 21 mg/mL. Muchof FXIII circulates in blood in association with fibrinogen.

[23, 24]

Platelet FXIII (an A2homodimer) constitutes approximately 50% of total FXIII activity in blood.Plasma FXIII has a long half-life of approximately 9-14 days. A similarity exists between a

portion of the carboxy terminal (C terminal) domain of FXIII and the receptor-binding region of

a2-macroglobulin. The complex of a2-macroglobulin and its substrate protease is removed fromthe circulation by binding to its receptor in the liver and other tissues; therefore, as has been

suggested, FXIII also may be removed from the circulation by a similar mechanism.[25, 26]

Some

features of the A and B chains of FXIII are listed below. Monoclonal antibodies and naturally

occurring inhibitors are used to elucidate structure-activity relationships.

Bone marrow cells, megakaryocytes, and monocytes/macrophages synthesize FXIII, with a

possible role for hepatocytes in the synthesis of subunit A. Subunit B is synthesized by the liver.

Tissue transglutaminase, the intracellular form of FXIII, consists of the A2subunit (an A2homodimer) and is present in a variety of cells including platelets, megakaryocytes,

monocytes/macrophages, and in the liver, placenta, uterus, prostate, and dermal dendrocytes.[27]

Red cells contain a transglutaminase that is activated by Ca2+

but is different from plasma

transglutaminase in its cross-linking activity and can cross-link fibrinogen as well as fibrin.

Trapped erythrocytes release FXIII when red cells lyse, providing additional cross-links to theaging thrombus.

[21]

Table. Some Features of the A and B Chains of Factor XIII(Open Table in a new window)

Properties A Chain B Chain

Plasma FXIII Has 2 A chains Has 2 B chains

Plasma level Approximately 15 mg/mL Approximately 21 mg/mL

Chains are free in plasma No. All bound to B chain and

present as an A2B2tetramer

Yes. Excess B chain present in

plasma as a B2dimer

Chain contains the catalytic

site

Yes No


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Chain is the carrier protein No Yes

Chain acts as a brake onFXIII activation

No Yes

Cellular FXIII Has 2 A chains (A2dimer) Has no B chains

Mutations can lead to

decreased FXIII activity

Yes Yes

Comparative biology shows that transglutaminases are distributed widely in nature and mayrepresent the prototype for the evolution of clotting enzymes.

[28]Partial homology of plasma

FXIII exists with several proteins including tissue and keratinocyte transglutaminases,

erythrocyte transglutaminase, and the hemocyte transglutaminase of the horseshoe crab and other

zymogens of the same family.

A recent example is from the crystal structure of transglutaminase of the Red Sea bream, which

shows that its active site and overall structure resemble that of human FXIII.[29]

Thesehomologies attest to conservation of the enzyme during evolution. Since the gene structures are

similar, it is believed that they evolved from a common ancestor. Subunit B contains 10

repeating "sushi" units linked by disulfide bonds; the function of the sushi unit is unknown.

Sushi structures are present in at least 26 proteins, including proteins in the horseshoe crab and inthe vaccinia virus.

Activation

Thrombin, generated by reactions initiated by activated tissue factor VII/factor IX pathways (as

illustrated in the first diagram below), leads to clot formation. Thrombin releases fibrinopeptideA from the a chain of fibrinogen, then fibrinopeptide B from the b chain of fibrinogen. Fibrin

monomers (formed following the release of fibrinopeptides) polymerize spontaneously; this isfollowed by development of a complex branching clot as a result of the actions of activated

FXIII (FXIIIa).[30]

The sequence of these final steps is found in the second chart below.


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Coagulation reactions leading to thrombin generation and

activation of factor XIII. Final steps in clot formation (fromarticle: Factor XIII).

Thrombin starts the process of FXIII activation by cleaving an activation peptide from subunit A.The subsequent Ca

2+-dependent dissociation of subunit B allows FXIII activation to proceed.

Calcium is important for activation of the zymogen (both FXIII and tissue transglutaminase

require Ca2+

), conformational changes, and opening of the catalytic site of FXIII to its substrate.

Calcium also provides physical stability as determined by x-ray crystallography, computermodeling, and other studies; all of the changes allow the active subunit A to perform its

functions optimally.[21, 31, 32]

When activated by thrombin, tissue FXIII functions in the same manner as plasma FXIIIa.Platelet FXIII undergoes nonproteolytic activation following the platelet activation-induced rise

in cytosolic Ca2+

. Activation of the red cell enzyme occurs upon exposure to Ca2+

, and red cellsthat are present in the fibrin clot lyse and release their FXIII as the clot ages. Several controls in

the complex activation process focus the actions of FXIIIa on fibrin rather than on fibrinogen.

Cross-linking of polymerized soluble fibrin by FXIIIa is the final step in hemostasis, as

illustrated in the following chart. For extensive details of this activation process, the reader isreferred to two recent reviews by Lorand.

[21, 28]Note the image below.

Activation of factor XIII and generation of insoluble cross-linkedfibrin. Adapted from Lorand L. Ann N Y Acad Sci. 2001;936:291-311.
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Role of FXIII in cross-linking and resistance to lysis

FXIIIa cross-links the lysine of one g chain in the fibrin polymer with the glutamine of another g

chain by transamidation, releasing ammonia in the process. Additional cross-links occur betweena-a chains, a-g chains, a chains-a2-plasmin inhibitor (a2PI), and a chains-fibronectin. As a result

of the extensive cross-linking actions of FXIIIa, the clot structure of fibrin polymers increases incomplexity from dimers to trimers to tetramers.

The g chains of fibrinogen and fibrin normally bind to the platelet membrane glycoprotein

IIb/IIIa complex. The same g chains are subject to cross-linking by FXIIIa; therefore, cross-linking also occurs between fibrin and the platelet membrane. Both plasma FXIIIa and platelet

FXIIIa cross-link fibrin polymers, but under physiologic conditions, platelet FXIII is believed to

play a minor role.[33]

Red cell FXIII is responsible for hybrid cross-linking of a-g chains, in

contrast to the actions of plasma FXIII.

Dysfibrinogenemias and dyshypofibrinogenemias result in alterations in fibrin (substrate for

FXIIIa), which can interfere with the ability of FXIII to cross-link fibrin. A reduction inavailable fibrin resulting from afibrinogenemia can have the same effect. Conversely, increased

fibrinogen levels have been identified as a risk factor for thrombosis.

Mechanisms of this risk were elucidated by a fibrinolysis assay containing purified components.

The assay showed that lysis of fibrin decreased as fibrinogen levels increased, and the presenceof a minor common variant of fibrin (g') is associated with accelerated cross-linking, which made

the clot resistant to proteolysis by both plasmin and trypsin. Increased clot stability also was

believed to result from increased concentration of FXIII in the clot. Non-cross-linked fibrin

potentiates activation of FXIII by thrombin; thus, the substrate potentiates its enzyme, furthercontributing to clot stability.

[24, 34, 35]

Cross-linking of a2PI to a chains of fibrin by FXIIIa brings the principal inhibitor of plasmin tothe site of the clot, ensuring resistance of the clot to proteolysis. Inhibition of a2PI in in vitro

systems leads to enhanced clot lysis. In humans, deficiency of a2PI results in a bleeding disorder

because of vulnerability of the fibrin clot to prompt degradation by plasmin. The formation ofhighly cross-linked a-fibrin polymers in the presence of high concentrations of FXIIIa produces

clots that are highly resistant to fibrinolysis.[36]

Fibronectin, an adhesive protein, is a large component (approximately 4%) of the proteins in a

fibrin clot, is present in plasma and cells, and is subject to cross-linking by both plasma and

cellular FXIII. Cross-linking of fibronectin to fibronectin and fibronectin to fibrin is

accomplished by FXIIIa, with fibronectin contributing to increased fiber size, density, andstrength of the clot. FXIIIa also cross-links actin to fibrin and actin to myosin. Cross-linking of

intracellular structural proteins is involved in clot retraction and cell migration. This complex gel

network created by the actions of FXIII plays an important role in wound healing, cell adhesion,and cell migration. All of these cross-linking reactions impart increased mechanical strength to

the clot, contributing to clot retraction and resistance of the clot to degradation by plasmin and

providing an explanation for the known plasmin resistance of older clots.


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Many other proteins function as substrates for FXIIIa, including von Willebrand factor (vWF),

factor V (FV), thrombospondin, gelsolin, vitronectin, vinculin, lipoprotein (a), and collagen

(FXIIIa cross-links collagen with fibronectin and vWF, attaches the clot to the vessel wall,impacts tissue repair, increases resistance of collagen to proteolysis, and modulates synthesis of

collagen by fibroblasts). Thus, FXIII plays a role in a wide array of cross-linking reactions

involving plasma proteins at the intracellular level, impacting many different functions.

Factors affecting level and activity of FXIII

When quantitative amine incorporation assays became available, healthy people were found tohave an 8-fold spread in FXIIIa activity.

[37]In recent studies of FXIII antigen and activity in

humans, no correlation was found between these two parameters. During the search for an

explanation, 23 unique FXIIIa genotypes were found. The Leu34 and Leu564 variants gave rise

to increased specific activity; the Phe204 variant lowered specific activity. Other mutations gaverise to low, high, or median FXIII-specific activity, and some variants had no effect.

[38, 39]

In a study of the variability of FXIII levels in racial groups, FXIII activity was found to be higherin Asian Indians (male and female) than in their Chinese counterparts, accounting for

approximately one fourth of the variability. Common genetic polymorphisms in the A and B

chains appeared to contribute to the differences.[40]

An influence exerted by acquired factors wasevident in the higher FXIII levels found in women who smoked 20 or more cigarettes per day

during a normal pregnancy than was found in nonsmokers, with a lesser drop in the second half

of pregnancy.[41]

Role of FXIII in pregnancy

In the latter half of pregnancy, some drop in FXIII levels is normal, but severe (homozygous)

FXIII deficiency is a cause of recurrent miscarriages. In a study of gestational tissues, FXIII wasfound in the decidual layer of the placenta, while FXIII secretion was evident in cultures of

round-shaped endometrial cells. A study of early (7-8 wk) gestational tissues obtained fromwomen without FXIII deficiency and from a woman who was homozygous for FXIII deficiency

showed poorly formed cytotrophoblastic shells and Nitabuch layers, along with absence of

FXIIIa in tissues obtained from the woman with FXIII deficiency. Low plasma levels of FXIIIappear to correlate with low placental levels of FXIII with poor trophoblastic development,

which may be the cause of spontaneous miscarriages.

It has been suggested that preventing miscarriage in patients who are severely deficient requires

FXIII supplementation beginning at approximately 5 weeks of gestation because FXIII,

fibrinogen, and fibronectin are necessary to anchor cytotrophoblasts invading theendometrium.

[42, 43]Reduced FXIII activity resulting from the Tyr204Phe mutation has been

associated with repeated miscarriages.[44]

Role of FXIII in wound healing

Physiologically, hyperpermeability induced by severe metabolic inhibition of porcine aortic

endothelial cells is prevented by FXIIIa, which is similar to the maintenance of endothelial


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barrier function by FXIIIa despite depletion of energy or during reperfusion of ischemic rat

hearts.[45]

In a different system, FXIII induced epithelial wound healing by increasing cell growth

by approximately 2.5 fold, leading to replacement of damaged cells.[46]

Smooth muscle cellmigration, an integral part of the healing process, is facilitated by FXIII. Migration of smooth

muscle cells in cross-linked fibrin gels was twice the migration seen in noncross-linked gels,

demonstrating the importance of the 3-dimensional clot structure created by cross-linking insmooth muscle cell migration.[47]

In humans, Fibrogammin was shown to contribute to thehealing of venous leg ulcers by reducing endothelial permeability.

[48]

Effects of other agents on FXIII

Nitric oxide (NO), an important diffusible molecular messenger, is increasingly recognized as

having an impact on coagulation proteins. Activity of plasma transglutaminase is inhibited by

NO via nitrosylation of critical thiol groups (reactive cysteine residue), resulting in inhibition ofboth g-chain cross-linking and insoluble clot formation. NO donors and carriers inhibit FXIII

activity in a dose-dependent manner, in a purified system and in plasma. Tissue

transglutaminases are involved in apoptosis, and inhibition of their activity by NO preventsapoptosis.

[49, 50]

Venoms and toxins can affect clot stability. Excessive bleeding resulting from envenomation canaffect the functions of FXIII in different ways. Acuthrombin A, one of two proteases in the

venom ofAgkistrodon acutus(five-pace snake), activates FXIII.[51]

Ancrod, obtained from the

venom ofAgkistrodonspecies, causes defibrination, thereby removing the substrate for FXIII.

A severe systemic bleeding disorder may develop several hours after initial contact with 2 types

of caterpillars in the Saturniidae family (from Brazil and Venezuela). Intracranial andintracerebral bleeding and renal failure may follow. In this case, FXIII reduction results from

generalized disseminated intravascular coagulation (DIC) induced by several activities directedagainst the hemostatic mechanism, including a FXIII proteolytic-urokinaselike activity.[52]

Tridegin, a peptide inhibitor of FXIII present in the saliva of an Amazon leech (Haementeriaghilianii) accelerates fibrinolysis by inhibiting FXIIIa; tridegin is under investigation as a

potential new antithrombotic agent. Destabilase, an enzyme present in the leech, hydrolyzes g-g

fibrin cross-links and breaks down blood clots.[53]

Simvastatin is a commonly used cholesterol-lowering agent. A nonantibody-mediated drug-

induced reduction in FXIII activity as part of a broader reduction in hemostatic activation hasbeen suggested to be the reason for the proven antithrombotic efficacy of simvastatin in clinical

trials.[54]

Blood samples were obtained sequentially every 30 seconds from a bleeding time cut in

patients with coronary artery disease, before and 3 months after simvastatin treatment. Sampleswere analyzed for the time-course drop in fibrinogen levels and activation of factors II, V, andXIII by quantitative Western blot analyses. Simvastatin, independent of its effects on cholesterol,

significantly reduced the rate of blood clotting, as evidenced by reduced formation of several

activation products including FXIIIa.

Several selective synthetic inhibitors have been shown to prevent the ability of FXIIIa tostabilize a clot, thereby reducing clot strength (clot stiffness, viscoelastic modulus) to


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approximately 20% of normal (values similar to those seen in patients with severe FXIII

deficiency). Rapid lysis of these clots occurred following in vitro exposure to thrombolytic

agents.[28]

Imidazolium derivatives, a new class of compounds, specifically inhibit both FXIII-induced formation of a-chain polymers and the incorporation of a2PI into the a chain of fibrin,

resulting in accelerated clot lysis.[10, 55]

Specific monoclonal antibodies to FXIII have provided similar benefits by reducing the

viscoelastic properties and by enhancing clot lysis. They also have been used to modify disease

states. The beneficial effect of the absence of cross-linked fibrin on pathophysiologic processeswas proven in an animal model of widespread thrombosis. FXIIIa deficiency induced in rabbits

by pretreatment with a specific monoclonal antibody before induction of a generalized

Schwartzman reaction protected them from the deleterious effects of widespread microvascular

thrombosis. The protection resulted from the ability of the fibrinolytic system to effectivelydegrade noncross-linked thrombi.

[56]These data add support to the author's speculation many

years ago of the potential use of drugs that inhibit cross-linking as a method of prophylaxis in

venous thromboembolic disease.

The biochemical basis and potential for using modifiers of fibrin stabilization in improved

thrombolytic therapies are discussed in a recent review by Lorand.[28]

Similar ideas have beenproposed by others, expanding on the importance of fibrin structure in thrombus formation and

dissolution.[57]

Prospective clinical trials must prove any thromboprophylactic efficacy of altering

fibrin structure using specific drugs.

Other functions of FXIII

Plasma and tissue transglutaminases have been reported to promote cell adhesion throughspecific integrins for 2 different tumor cell types, MOLT-3 human lymphocytelike leukemia

and melanoma cells and SW480 colon cancer cells transfected with a ligand.

[58]

In contrast, FXIIIdid not stimulate growth of cultured human tumor cells.[59]

An intriguing observation is the

potential use of subunit A of FXIII and FXIII activity as a tumor marker in malignant braintumors; its presence may distinguish benign from malignant brain tumors.

[60]Recently, it was

shown for the first time that intranuclear accumulation and cross-linking activity of FXIIIa

occurred in maturing monocytes, supporting the hypothesis that FXIIIa may be involved in cellproliferation/differentiation, chromatin structure remodeling, and even cell death.

[61]Further data

are needed to unravel the role of FXIII in malignancies.

An unexpected role has been postulated for FXIII in degenerative brain disorders. In Alzheimer

disease and spongiform encephalopathies, the brain contains fibrils that develop from native

proteins containing a discordant a helix. Human FXIII was found to form fibrils in bufferedsaline, suggesting that FXIII, in addition to several other proteins, can be a source of thisabnormal fibrillar protein.

[62]

Possible interactions between deficiencies of FXIII and thrombin-activatable

fibrinolytic inhibitor


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Thrombin-activatable fibrinolytic inhibitor (TAFI), a single-chain carboxypeptidase Blike

zymogen, is activated by thrombin to become activated TAFI (TAFIa).[63]

The importance of

TAFIa in fibrinolysis is emphasized by the fact that the conversion of only 1% of the zymogen toTAFIa is sufficient to suppress fibrinolysis by approximately 60%.

TAFIa suppresses fibrinolysis by removing C-terminal lysine and arginine residues exposed inthe partially degraded fibrin clot produced by plasmin. Removal of C-terminal lysine residues

from fibrin reduces the rate of plasminogen activation by a number of mechanisms, attenuating

fibrinolysis. This effect is counterbalanced in normal plasma by activation of protein C, whichhas profibrinolytic properties because of its ability to suppress thrombin generation via its major

effect of degrading activated factor V (FVa), and to a lesser extent, activated factor VIII

(FVIIIa).[63, 64, 65]

As illustrated in the chart below, a delicate balance usually exists between thrombus formation

and thrombus resolution; thrombin secures survival of the thrombus created by its action on

fibrinogen by activating TAFI, thereby inhibiting fibrinolysis. Cross-linking of fibrin induced by

FXIIIa (activated by thrombin) renders the clot insoluble. FXIII deficiency results in absence ofcross-linked fibrin, leading to premature lysis of the clot by the fibrinolytic system; adverse

consequences result, including bleeding. Theoretically, a deficiency of TAFI leading todecreased suppression of fibrinolysis (enhanced clot lysis) can potentiate bleeding resulting from

FXIII deficiency (also associated with enhanced clot lysis). Note the image below.

Postulated interaction between factor XIII and thrombin-activatable fibrinolytic inhibitor.

Cell surfacedirected hemostasis

The concept of coagulation as a waterfall or cascade effect has been acknowledged for a long

time, with platelets and other cell surfaces providing the anionic phospholipids needed for

complex formation, so that reactions can proceed efficiently. One review proposed thatcoagulation is essentially a cell surfacebased event.

[66]Platelet FXIII is positioned appropriately

to influence the process. (See the diagram below.)
http://refimgshow%284%29/


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Cell surfaceddirected hemostasis. Initially, a small amount ofthrombin is generated on the surface of the tissue factorbearing (TF-bearing) cell. Following

amplification, the second burst generates a larger amount of thrombin, leading to fibrin (clot)

formation (from article: Factor XIII). Adapted from Hoffman and Monroe. Thromb Haemost.2001;85(6):958-65.

Conclusion

Much work is needed, even in the clinical arena, to clarify the relationship between the exact

levels of FXIII and hemorrhagic or thrombotic phenotypes. Establishing an international registry

of patients deficient in FXIII would be of value in improving understanding of the proteanmanifestations of this uncommon disorder.

Frequency

United States

Overall estimated frequency of the autosomal recessive disorder involving a severe deficiency of

subunit A is approximately 1 case per 2 million population. Previously, consanguinity was

believed to be necessary, but the detection of compound heterozygotes by the application ofmolecular techniques is changing that perception. Approximately 200 cases of FXIII deficiency

have been described thus far.[67]

See Other Problems to be Considered for a discussion ofacquired FXIII deficiency related to diseases or inhibitors.

International

FXIII deficiency has been reported in many ethnic groups around the world, including persons

from Canada, Europe, India, Israel, Japan, Kuala Lumpur, Pakistan, Papua New Guinea, South

America, Thailand, Turkey, and the United States.

Diagnosis of disorders of FXIII inhibitors, which may have been missed in the past, is increasingas more laboratory support becomes available around the world. An increasing use of isoniazid(INH) to combat a worldwide rise in incidence of tuberculosis could contribute to an increased

incidence of FXIII inhibitors in patients.

Variability in the distribution of mutations is exemplified by existing data, ie, significant ethnic

heterogeneity was found in a Brazilian population in which the Val34Leu mutation was present


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in 51.2% of American Indians, 44% of whites, 28.9% of Africans, and in only 2.5% of Japanese

Asians.[68]

Mortality/Morbidity

Umbilical bleeding starting in the first few days after birth, recurrent intracranial bleeding, andrecurrent early miscarriages are hallmarks of FXIII deficiency.

Approximately 30% of central nervous system (CNS) bleeding is recurrent, and approximately50% of CNS bleeding may be fatal, but the severity of bleeding varies from family to family.

Posttraumatic bleeding may be immediate, delayed, or recurrent. Traumatic joint bleeding may

develop. Poor wound healing has been described, although this is not a universal finding.

Cryoprecipitate and fresh frozen plasma (FFP) provide a source of FXIII for most patients. All

plasma-derived products carry risks of transmitting hepatitis, HIV, parvovirus B19, transfusion

transmitted virus (TTV), and prion-induced (new variant Creutzfeldt-Jacob disease [nvCJD])

illnesses (see Complications and Medscape Reference articleFactor VIIIfor more information).Plasma-derived FXIII concentrates are being tested at centers. Recombinant factor XIII (rFXIII)

subunit A concentrates are yet to be tested widely.

Development of FXIII inhibitors (alloantibodies or autoantibodies) is associated with significant

morbidity and mortality.

Pregnant women with FXIII deficiency have a significant risk of miscarriage, placental

abruption, and postpartum hemorrhage without prophylaxis.[69]

Race

No predilection exists for FXIII deficiency. FXIII deficiency has been reported widely. The

restriction of certain polymorphisms to specific populations should be expected.

Sex

Since it is an autosomal disorder, homozygous FXIII deficiency occurs in either sex. Acquiredinhibitors to FXIII can present in either males or females.

Age

Physiologically, reduced levels of FXIII are found in healthy newborns, with a gradual rise inlevels into the reference range. Premature infants have lower values than full-term neonates.

FXIII levels drop in the latter half of a normal pregnancy.

Severe FXIII deficiency may present with bleeding from the umbilical cord after birth. Easy

bruising and delayed and recurrent bleeding after trauma begin in childhood. Oral bleeding canbegin with teething and cuts or abrasions to the lips, tongue, and frenulum. Bleeding remains a
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problem throughout life and requires replacement therapy. FXIII deficiency acquired as a result

of autoantibodies has been reported in the older population, as has acquired hemophilia A. Both

drug-induced autoantibodies and alloantibodies have been reported in patients who are severelydeficient and receiving replacement therapy.

History

The following symptoms should trigger an evaluation for FXIII deficiency:

Spontaneous miscarriages occur early in pregnancy.

Bleeding from the umbilical cord has been reported to develop from 1-19 days after birth.

Easy bruising and soft tissue bleeding, particularly in association with trauma, occur as

the infant starts to ambulate. Bleeding following trauma may be immediate, delayed,and/or recurrent.

CNS hemorrhage is common, recurs in approximately 30% of patients, and may be the

initial manifestation in patients with severe FXIII deficiency.

CNS bleeding may be preceded by head trauma in children, while adults may develop aCNS bleed in the absence of obvious trauma.

Symptoms typical of any CNS event may be present, eg, headaches, seizures, vomiting,

and focal neurologic defects. Symptoms may be acute at onset or may be superimposedon residual findings of a past bleed.

Menorrhagia and intra-abdominal bleeding during menses may be present.

Bleeding into joints may be precipitated by trauma. Although reports exist of recurrenttarget joint bleeds, destructive changes in the joints are uncommon.

[2]Spontaneous joint

and extensive muscle bleeding, characteristic of patients with severe hemophilia, are

uncommon in patients with severe FXIII deficiency.

The severity of bleeding is variable. An unusual example is the history of a very mild

bleeding disorder in 2 sisters despite severely reduced levels of FXIII (< 1%). One of thesisters had 2 successful pregnancies without product replacement (see Causes for

details).[70]

Poor wound healing, although described, is less common.

Heterozygous parents of a propositus with severe bleeding usually are asymptomatic,

although some cases of bleeding in heterozygotes have been reported.

Development of alloantibodies is a serious complication that results in increased bleedingand a lack of response to usual therapy. This condition can be fatal (see Other Problems

to Be Considered for more information).

Autoantibodies to FXIII are an acquired cause of a bleeding diathesis. A detailed drug

history is essential in assessing the possible contribution to inhibitor development. As the

frequency of tuberculosis rises worldwide and the use of INH increases, the number ofpatients with inhibitors may increase (see Other Problems to Be Considered for more

information).

Patients may have acute and/or chronic viral illnesses transmitted by less pure products,

such as FFP or cryoprecipitate, that are used to treat bleeding. HIV-related illnesses,

AIDS, chronic hepatitis, progressive hepatic failure, and parvovirus-related illnessespresent in the usual manner.


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Physical

Physical findings depend on the site at which bleeding develops and include the following:

Bleeding from the umbilical cord after birth usually manifests with persistent oozing,

which may start a few days after birth. Findings associated with CNS bleeding depend on the location of the bleeding. Trauma

may precede the event, with additional findings. A new CNS bleed may be superimposed

on residual findings related to a prior bleed.

Findings in patients with bruising and soft tissue bleeding are similar to those seen inother patients; it is uncommon to find the large hematomas or joint bleeds characteristic

in patients with severe hemophilia.

Patients may present with vaginal spotting or bleeding during early pregnancy, preceding

a spontaneous miscarriage.

Persistent, delayed, or recurrent bleeding may occur at sites of trauma or surgery.

Poor wound healing may be noted.

Acquired causes of FXIII deficiency, such as DIC and liver disease, present in a well-recognized manner.

Causes

To date, most identified mutations leading to severe FXIII deficiency and a bleeding disorder

involve subunit A, with very few mutations reported involving subunit B. The gene for subunit A

is located on chromosome 6 bands p24-25. The gene is 160 kilobases in length and has 15 exonsand 14 introns with specific structural and functional domains. Catalytic activity is encoded in

the second exon, and the active cysteine is encoded by the seventh exon. The 2 Ca2+

-binding

sites and a thrombin-inactivation site have been identified at other locations. The gene forsubunit B is located on chromosome 1 bands q31-32.1, is 28 kilobases in length, and has 12exons and 11 introns.

[9, 71](See the image below.)

Gene, messenger RNA, and protein for subunit A of factor XIII.

Adapted from Reitsma PH. In: Hemostasis and Thrombosis: Basic Principles and ClinicalPractice. Lippincott Williams & Wilkins; 2001:59-87 and from Roberts HR, Monroe DM III,Hoffman M. In: Williams Hematology. McGraw-Hill Professional; 2001:1409-34.

Detailed characteristics of complementary ribonucleic acid (cRNA) and messenger ribonucleic

acid (mRNA) of the placental subunit A are known. The presence of an acetylated amino

terminal end and the absence of glycosylation and disulfide bonds apparently are features typical


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of secreted cytoplasmic proteins. The presence of these characteristics makes it conducive for

subunit A expressed in yeast systems to make a recombinant product.

Substitutions in the core domain of the enzyme, affecting highly conserved residues, result in a

serious defect in structure and function. Missense mutations in the A chain are a common cause,

accounting for approximately 50% of cases of severe FXIII deficiency. The defects result in anabsence of subunit A protein but also are accompanied by a reduction in subunit B carrier protein

(type II defect).

Nonsense mutations are an equally common cause of A chain defects, resulting in a frameshift-

type, splice-type, or termination-type mutation. The few defects that have been reported in the B

chain lead to a deficiency of the carrier protein (subunit B), which then leads to instability andreduction of plasma subunit A levels despite the presence of functional intracellular subunit A

(type I defect).[72]

Therefore, patients who are homozygous for subunit B mutations have a

bleeding disorder. Most recently, impaired intracellular transport from the endoplasmic reticulum

to the Golgi apparatus, with failure of secretion of the truncated FXIII subunit B produced by a

single-base deletion, was reported to be the cause of severe FXIII deficiency in 3 unrelatedpatients.[73]

Many kinds of mutations have been (and continue to be) identified, with some mutations unique

to certain families. The finding of compound heterozygotes has eliminated the mandatory search

for consanguinity in all parents of patients with severe FXIII deficiency.[74, 75, 44]

An unusual mutation has been described in 2 Finnish sisters with a very mild bleeding disorder.

One sister had 2 successful pregnancies without regular replacement therapy. The sisters had nodetectable subunit A activity (< 1%) using plasma screening tests; however, using the 3H-

putrescine incorporation assay, subunit A showed 0.35% of normal activity, with partial g-g

dimerization of fibrin in clotted plasma. A full-length subunit A was detected in the patients'platelets using Western blot analysis.

The sisters had an Arg661-->stop mutation on one allele and a T-->C transition on the otherallele. These data showed that a mutation in the splice donor site of intron C can result in

different variant mRNA transcripts and that small amounts of correctly processed mRNA can

produce a type of FXIII that can produce, at least, dimerization of fibrin, thus minimizing theclinical consequences.

[70]

Various reported mutations are spread throughout the gene coding for FXIII without specific hot

spots. In many patients, low steady-state mRNA levels have been found, which result ininefficient production of the abnormal protein.

[10]

Data in the literature conflict regarding the impact of the common FXIII subunit A Val34Leumutation (associated with higher plasma transglutaminase activity) on thrombotic disease. Note

the following:

The Val34Leu mutation continues to be studied in different populations because current

data provide conflicting evidence about its causal role in coronary artery disease. The


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Val34Leu mutation appears to protect whites but not Asian Indians from myocardial

infarction. However, in the Asian Indian population in Britain, a strong link was found

between FXIII subunit B levels and risk factors for cardiovascular disease and, possibly,insulin resistance.

[76]

In separate studies, a higher frequency of the Val34Leu mutation was found in whites

with primary intracerebral hemorrhage; however, the mutation reportedly was associatedwith a reduction in brain infarcts.

A possible cooperative interaction between the Val34Leu mutation and other knownthrombophilic mutations also has been explored. Note the following:

In a study of patients from southern France, a higher than usual odds ratio was found forthe association between carriers of an angiotensin receptor mutation and coronary artery

disease, but no association was found between the disease and any of the FXIII

polymorphisms that were studied.[77]

A study of the contribution of the Val34Leu mutation to thrombotic risk in a large

number of carriers of factor V Leiden (who were relatives of thrombotic propositi withfactor V Leiden) found a very modest contribution of the Val34Leu mutation to venous

thrombotic disease.[78]

This study contrasts with a report of a protective role of the mutation in venous

thrombosis.[79]

A recent review discusses the possible role of FXIII in vascular diseases.[80]

The FXIII

Val34Leu mutation does not appear to influence the induction or modification of thecourse of inflammatory bowel disease.

Genetic polymorphisms affecting both the A and B subunits have been reported, but becausethey do not involve conserved amino acids or are not important for protein structure, they do not

result in FXIII deficiency and bleeding. Based on an analysis of polymorphisms in the gene forFXIII subunit A and their products in a northern Portuguese population, it has been stated thatthe evolutionary order of appearance of the main protein alleles for FXIII is 1B-->2B-->1A-->2A

and that intragenic combinations are likely to have played a role in the molecular diversity in the

main FXIII subunit A alleles.[81]

Genetic polymorphisms and, particularly, intragenic polymorphisms are useful in genetic

counseling of families with unknown mutations. For example, 80% of whites are heterozygousfor a tetrameric repeat in intron 1 of subunit A, which can help differentiate defects in subunit A

from defects in subunit B.[9, 10, 71, 4]

Some polymorphisms are universal, while others appear to be

restricted to particular ethnic groups. The latter situation will change as ethnic intermarriages

increase in this global society. Families with severe FXIII deficiency associated with a seriousdisabling bleeding disorder have access to all of the genetic tools available to patients with

hemophilia A and B.

Disorders of fibrin stabilization can affect the activity of FXIII or its substrates fibrin and

fibrinogen. A proposed classification of disorders leading to a positive urea solubility test result

is presented below.


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Disorders of fibrin stabilization (positive urea solubility test) are as follows:

Abnormalities of FXIII (enzyme) are as follows:

o Genetic mutation - (1) Subunit A, (2) subunit B, (3) subunit A and B

o Acquired - (1) Decreased production, ie, liver disease; (2) increased loss due to

excessive activation, ie, DIC, exposure to snake venoms and caterpillar toxins; (3)secondary to inhibitors, ie, alloantibodies and autoantibodies

Abnormalities of the substrate for FXIII (fibrin/fibrinogen) are as follows:

o Genetic mutation - (1) Afibrinogenemia, (2) dyshypofibrinogenemia

o Acquired - (1) Decreased production, ie, acute massive hepatic necrosis or severe

chronic liver disease, (2) increased loss resulting from defibrination syndromes,

ie, DIC, exposure to snake venoms and caterpillar toxins, and systemic

hyperfibrinolysis (drug induced or disease induced)

Although gene therapy has not been used as a treatment modality in patients with FXIII

deficiency thus far, the reader is referred to a review of gene therapy in the hemophilias[82]

and a

review on the use of gene therapy in malignancy, which provides an excellent overview of theadvantages and disadvantages of various approaches to gene therapy.[83]

Differential Diagnoses

Disseminated Intravascular Coagulation

Dysfibrinogenemia

Factor II

Factor IX

Factor V

Factor VII

Factor VIII Factor XI Deficiency

Glanzmann Thrombasthenia

Menorrhagia

von Willebrand Disease

Proceed toWorkup

Laboratory Studies

The following routine tests are the first step in the evaluation of any bleeding disorder: aPTT,

PT, thrombin-clottable fibrinogen level, platelet counts, and bleeding time (the latter afterascertaining that the patient was not on antiplatelet drugs for at least the preceding 5 d).

However, these tests cannot be used to screen for FXIII deficiency because the results would be

within reference ranges in a patient with isolated severe FXIII deficiency.[3]
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The next test performed is a qualitative screening test for severe FXIII deficiency that assesses

clot solubility in 5M urea or 1% monochloroacetic acid. If the thrombin and Ca2+

-induced clot

lyses within a few hours, severe FXIII deficiency is suggested provided fibrinogen levels arequalitatively and quantitatively within reference range. Excluding hypofibrinogenemia and

dysfibrinogenemia is important, since these conditions cause false-positive results on the 5M

urea solubility test. The thrombin-clottable fibrinogen test can be used to excludehypofibrinogenemia and dysfibrinogenemia.

If the 5M urea solubility test demonstrates positive results, this finding should be confirmed byquantitating FXIII activity using a monodansylcadaverine or putrescine incorporation assay,

which must be performed by laboratory personnel with expertise.

TEG is an old method used to assess clotting and lysis of fresh whole blood, and it has been used

as an early tool in the initial evaluation, and as a simple laboratory test, of the mechanical

strength (effect of FXIII) of fibrin sealants.[94]

However, TEG cannot supplant any of the

qualitative or quantitative tests discussed in this section.

A new sensitive assay used to quantitate FXIII activity is based on monitoring the amount of

ammonia (NH3) released by using glutamate dehydrogenase and nicotinamide adeninedinucleotide phosphate during the transamidation reaction (cross-linking) by FXIII. Note the

following:

Reportedly, this test is sensitive over a wide range of activities, from a low of 1 U/L

(0.1%) to a high of 470 U/L (47%), with an impressive coefficient of variation (CV) of

less than 8%, even at very low FXIII activity levels. Note that a low CV in the low rangeof FXIII activity is a desirable feature of assays of this enzyme.

[95]

Compared to the cumbersome conventional quantitative amine incorporation assays, the

new method appears to be simple, rapid, and reproducible not only in the assessment ofinherited or acquired reductions of FXIII activity levels but also in the ability to measureincreased FXIII activity levels resulting from certain mutations. The test fulfills the need

for a simpler method to quantify FXIII activity.

The same group also has published results of a simple, quick (2 h), 1-step, enzyme-linkedimmunoassay (ELISA) to determine the presence of the plasma tetramer (A2B2). Results

demonstrated high sensitivity and low CVs within batches and in day-to-day

variations.[96]

Another new and sensitive colorimetric assay based on incorporation of 5-(biotinamido)

pentylamine into fibrin/fibrinogen was compared to a photometric method based on ammoniarelease and an ELISA of FXIII subunit A to quantitate FXIII activity. The test was shown to be

sensitive to both reductions and increases in activity; the increases resulted from the FXIII

Val34Leu mutation.[4]

In addition, a2PI and plasminogen activator inhibitor-1 assays should be performed to exclude

abnormalities in the fibrinolytic pathway, which accelerate clot lysis.


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Sodium dodecylsulfate polyacrylamide gel electrophoresis under reducing conditions has been

used to assess the presence of cross-linked g or a chains of fibrin, which is a reflection of FXIII

activity. The studies must be performed by laboratory personnel with special expertise.

If the presence of an inhibitor is suspected in a patient with a positive urea solubility test result,

the next step is to repeat the urea solubility test with mixtures containing varying proportions ofpatient and normal plasma to differentiate between a deficiency or an inhibitor as the cause of a

positive result. Since FXIII activity is present in serum, serum also may be substituted for plasma

in the test.

Semiquantitation of the susceptibility of the fibrin clot to fibrinolysis can be obtained by adding

iodine-125-labeled fibrinogen, tissue plasminogen activator, thrombin, and Ca2+

to the patient'splasma, with measurement of the time to 50% clot lysis. This method is useful in evaluating

inhibitors but must be performed by laboratory personnel with special expertise.

See Lorand for a recent review of further details of the sequence of necessary testing to confirm

the presence of a FXIII inhibitor.

[87]

Acquired systemic disorders, including decompensated DIC and liver disease, require standard

tests to confirm the diagnosis.

Caution is warranted in obtaining blood samples for any coagulation assays from heparinized

central lines because of the effect of large amounts of heparin on any coagulation test that

depends on thrombin generation.

Prenatal diagnosis is as follows:

Use of several diagnostic procedures has been well established in the evaluation ofpatients with FVIII and factor IX (FIX) deficiencies. In one case report, a short tandem

repeat marker that was closely linked to subunit A was used antenatally to identify thepresence of a severe bleeding disorder in a subsequent pregnancy in a family in which an

older sibling had severe FXIII deficiency.[97]

Chorionic villous sampling at approximately 10-12 weeks of gestation or amniocentesisat 16-20 weeks of gestation can be performed to obtain fetal cells for DNA analysis or for

linkage studies. If DNA analysis cannot be performed, fetal blood obtained by fetoscopy

at approximately 20 weeks of gestation can be used. In general, these procedures carry

risks ranging from a low of approximately 0.5% maternal-fetal complications to a high ofapproximately 1-6% fetal death for fetoscopy.

Perform these procedures only after intense genetic and obstetric counseling of the

parents.

Perform liver function tests; kidney function tests; HIV-1 and HIV-2 antigen and antibody tests;

hepatitis A (HAV), hepatitis B (HBV), hepatitis C (HCV), hepatitis D, and hepatitis Eantigen/antibody levels; and other tests as needed.

Assess a-fetoprotein levels and other tumor markers as needed in patients with chronic hepatitis.


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FXIII, which is involved in wound healing and angiogenesis, may be detectable by highly

sensitive chemiluminescent ELISAs in tiny volumes of tear. This concept may provide a tool for

monitoring FXIII subunit and complex levels in pathological conditions.[98]

Imaging Studies

MRI, CT scan, and ultrasound have been used to localize, quantify, and serially monitor the

location and response of bleeding to specific therapy. Perform other imaging tests as needed to

diagnose associated diseases.

Other Tests

Perform ECGs as needed.

Procedures

Diagnostic amniocentesis, chorionic villous sampling, or fetoscopy may be performed duringpregnancy. Perform other routine procedures when indicated. Perform arthrocentesis only when

infection is suggested. Any invasive procedure requires the appropriate factor replacement.

When indicated, perform other procedures, such ascolonoscopy,in persons without hemophilia.

Evaluate persistent GI tract bleeding without an apparent cause using endoscopy and

colonoscopy to exclude underlying lesions. Persistent genitourinary tract bleeding requiresevaluation for nephrolithiasis, tumors, or obstruction. If a biopsy is needed, patients require

replacement therapy prior to and following the procedure until the biopsy site has healed.

Invasive lifesaving procedures should be performed in patients with inhibitors only in concertwith appropriate treatment.

Medical Care

FXIII replacement is used to treat bleeding, to prevent perioperative bleeding during elective

surgical procedures or, prophylactically, to prevent recurrent bleeding, as in CNS or jointhemorrhages. Serial monitoring of achieved FXIII levels is essential to document the adequacy

of any therapy.

Prompt and adequate therapy for acute bleeding is essential along with immobilization of theaffected sites and pain relief. Most patients receive FFP or cryoprecipitate to treat bleeding.

Information regarding the amount of FXIII present in either of these products usually is notavailable; therefore, monitoring the adequacy of FXIII levels is essential.

Two intermediate-purity FXIII concentrates are being tested in the United States and areavailable in other countries. Note the following:
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Virus-inactivated FXIII concentrates made from human plasma or placenta are an

improvement over traditional products.

Human factor XIII concentrate (Corifact by CSL Behring) is now approved in the UnitedStates. The brand name Fibrogammin P (CLS Behring) is the plasma-derived virus-

inactivated concentrate marketed in Europe, South America, South Africa, and Japan. A

second FXIII concentrate (Bio Products Laboratory, Elstree, Hertfordshire, UK) isavailable on a per patient request.

Factor XIII A-subunit, recombinant (Tretten) was approved by the FDA in December 2013.Approval was based on results from a clinical study that demonstrated the safety and efficacy of

rFXIII A-subunit. The phase 3 trial included 41 patients and showed that when compared to an

historic control group of individuals who did not receive routine FXIII infusions preventive

treatment with monthly 35 IU/kg rFXIII A-subunit injections significantly decreased the numberof treatment-requiring bleeding episodes.

[99]

The long half-life of FXIII of 6-19 days and the hemostatic efficacy of even small amounts of

FXIII of approximately 5% allow replacement therapy to be administered every 4-6 weeks. AnFFP dose of 2-3 mL/kg may be effective for up to 4 weeks.[100, 101]

The dose of concentrate in

adults with deficiency is 35 U/kg every 4 weeks.[102, 103, 104]

A paucity of data exists concerning the pediatric population. Hemostatic evaluation following a

head trauma-induced large subcutaneous hematoma associated with recurrent postsurgicalbleeding led to a diagnosis of severe FXIII deficiency in a 22-month-old boy. Following initial

therapy, subsequent replacement with an FXIII concentrate dose of 50 U/kg every 5 weeks was

sufficient to prevent rebleeding and allow healing.[105]

Serial monitoring of actual levels achieved

is important in children to determine adequacy of any therapy.

Minor bleeding, as from cuts and abrasions, may respond to conservative measures, such aspressure, ice, and use of antifibrinolytic drugs. Avoidance of trauma and nonsteroidal anti-inflammatory drugs (NSAIDs) is helpful in reducing bleeding events.

Several reports exist of the use of FXIII in unusual circumstances. Note the following:

Effectiveness of normalizing FXIII levels in the treatment of a cerebrospinal fluid leak,which started 2 weeks after removal of a meningioma, was reported in a Japanese

patient.[106]

The potential use of transglutaminases to mechanically stabilize and allow cultured

epithelial autografts to take when used to repair extensive skin wounds supports apossible role of FXIII in the formation of de novo dermoepidermal junctions, thereby

facilitating permanent skin replacement.[106]

Improved stability of surgical wounds has been reported following infusion of FXIIIconcentrates.

Although a few reports exist concerning the use of FXIII replacement in patients with

scleroderma, Henoch-Schnlein purpura, and malignancies, the value of suchreplacement therapy remains to be established by proper clinical trials.

[10, 107, 108, 109]


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Patients with acquired inhibitors to FXIII should be treated using well-established principles of

therapy. Note the following:

FXIII dose depends on the characteristics of the inhibitor. One patient was treated

preoperatively using a 10-fold dose of FXIII concentrate (350 U/kg) followed by a

similar postoperative dose resulting in adequate hemostasis after coronary bypass graftsurgery.[104]

In addition to administering an FXIII concentrate whenever available, treat the

underlying disorder and, when appropriate, use immunosuppressive agents, including thenewer B-cell-directed monoclonal antibodies.

Note that spontaneous disappearance of acquired inhibitors is part of their natural history,

and the use of milder less toxic immunomodulators, such as steroids, may suffice.

The proper choice of agent is dictated by clinical circumstances. Simple immediateancillary measures of ice, pressure, ace wrap, immobilization of the affected joint, and

avoidance of NSAIDs must not be forgotten.

The complexity of required treatment is exemplified by a patient with an INH-induced

inhibitor in whom INH was discontinued, cryoprecipitate and FXIII concentrate wereadministered, the patient underwent plasma exchanges and treatment with an

immunoadsorption column to reduce the inhibitor's titer, and immunosuppressives wereadministered before hemostatic success was achieved.

[89, 87, 91]

To date, prophylactic factor replacement has been undertaken mainly in patients with intracranial

bleeding or recurrent miscarriages caused by severe FXIII deficiency. Successful prevention ofrecurrent joint bleeds also has been accomplished using periodic transfusions of FFP and

cryoprecipitate.[2]

FFP can be administered in a dose of 2-3 mL/kg every 4 weeks.

A literature review of bleeding risks and reproduction among patients with severe FXIII

deficiency suggests that patients with clinically significant bleeding should start receiving factorreplacement therapy in childhood to reduce early mortality from hemorrhages and to allowpatients to reach adulthood. During pregnancy, monthly replacement was found to be effective in

preventing miscarriages.[110]

However, both short-term benefits and potential long-term adverse

consequences of prophylactic use of these products must be discussed, with full patientparticipation in all decision making.

Advances in the types of available products improve care. Addition of Tween 20 makes areduction of the generation of soluble and insoluble aggregates of rFXIII possible when rFXIII is

subjected to freezing and thawing or agitation.[111]

Another advance in the technology relates to

solving problems faced during freeze-drying and storing the dry solid. Improvement in storage

stability of therapeutic proteins has obvious advantages for both storage and transport.[112]

Pooled plasma treated with solvent-detergent (PLAS+SD) is available to treat any condition in

which FFP typically is used and for which no factor concentrate is available. Viral inactivationusing the solvent-detergent (SD) process has been used in preparation of coagulation factor

concentrates in the past. In vitro treatment of donor plasma with 1% of the solvent tri(n-butyl)

phosphate (TNBP) and 1% of the detergent Triton X-100 leads to significant inactivation of abroad spectrum of lipid-enveloped viruses. Note the following:


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Studies of viral inactivation using the SD process show significant inactivation of the

human pathogenic viruses hepatitis B and C and HIV. Other lipid-enveloped viruses (eg,

Sindbis virus, bovine viral diarrhea virus) also have been used to monitor inactivation.

PLAS+SD is ABO blood type specific, and SD-treated plasma should be ABO

compatible with the recipient's red cells.

The frozen product is supplied in 200-mL bags. Each 200-mL bag has been demonstratedto raise factor levels by approximately 2-3%, with 4-6 bags raising the factor level of a70-kg person by approximately 8-18%.

Monitoring of specific factor levels before and after product infusion is important to

ensure that hemostatically adequate levels are achieved and maintained to provideadequate hemostasis.

Antifibrinolytic agents are not used commonly to treat patients with FXIII deficiency but may beused as ancillary therapy. Note the following:

The hemostatic plug formed in the presence of adequate levels of FXIII at the time of

surgical trauma (as with dental procedures or with mucosal bleeding) can be preserved byinhibiting fibrinolysis with -aminocaproic acid (EACA; Amicar) or trans-p-

aminomethyl-cyclohexane carboxylic acid (AMCA; also termed tranexamic acid;Cyklokapron) administered orally or, if needed, intravenously. EACA has been

administered in a dose of 5 g orally or intravenously slowly prior to the surgical

procedure, along with a dose of the appropriate FXIII replacement. This is followed by a

maintenance dose of 1 g/h postoperatively until it is appropriate to start tapering the doseover the next several days.

AMCA is administered in a dose of 1.5 g intravenously every 6-8 hours and tapered, as

needed; however, it is not available in the United States.

Antifibrinolytic agents also can be used as a mouthwash for oral bleeding and have been

used to stop local intracavitary oozing.

Antifibrinolytic agents are contraindicated in patients with hematuria because of the

possible risk of development of a firm occluding clot in the ureters when administeredsimultaneously with factor replacement. The drugs are not useful in the treatment of joint

bleeding (seeFactor VIIIfor more information).

In recent years, the use of NSAIDs to relieve pain has increased in patients with bleeding

disorders. Although they provide relief from inflammatory pain, patients experience increased GI

tract or other bleeding because of the impact of the drugs on primary hemostasis, and theyrequire additional FXIII replacement to control bleeding. The problem is magnified by the

availability of over-the-counter NSAID pain relievers. Non-NSAIDs, such as acetaminophen and

codeine-type analgesics, are much less effective, and some are addictive.

Routine dental care is of the utmost importance in maintaining dental hygiene.

Other routine care, such as mammography in women older than 50 years orcolonoscopyfor

patients older than 50 years, must be provided as in nonbleeding patients.

Surgical Care
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All elective procedures require proper perioperative management. Note the following:

Patients with severe FXIII deficiency require FXIII replacement both preoperatively andpostoperatively. Levels of as little as 3-5% may be sufficient to provide adequate

hemostasis, and a single dose is sufficient to last several weeks unless excessive blood

loss occurs. Serial factor levels must be performed to ensure adequacy of FXIII levels. Procedures such as endoscopies, although considered routine for unaffected individuals,

require preprocedural product replacement so that patients do not bleed during or

following a needed biopsy. Postbiopsy replacement must continue until the biopsy sitehas healed.

Dental extractions or mucosal procedures can be handled using a single preprocedure

dose of FXIII along with Amicar or AMCA. A standardized approach to dental

extractions, as has been proposed for patients with hemophilia, may be used in patientswith FXIII deficiency. Continuing antifibrinolytics on an outpatient basis for several days

after a dental extraction is routine practice, with gradual tapering of dosage.

Avoidance of NSAIDs and other platelet-inhibiting drugs perioperatively is essential to

minimize bleeding risk. Ice packs and pressure are always useful when feasible. Application of fibrin glue as an ancillary measure is useful in helping control bleeding at

surgical sites. Fibrin glue consists of a mixture of fibrinogen, thrombin, and FXIII used tocross-link freshly formed fibrin. Cryoprecipitate also has been used as a source offibrinogen and FXIII, with the use of bovine thrombin to clot fibrinogen. Some

preparations also incorporate antifibrinolytic agents to prevent clot lysis. In particular,

fibrin glue has been useful in orthopedic surgery and with surgical procedures in patientswith FXIII inhibitors. Bovine thrombin may elicit antibodies.

Bleeding from suture holes is a complication in a variety of invasive vascular procedures

(surgery, radiologic procedure, coronary angiography). In an experimental porcine

vascular graft model, fibrin sealant containing FXIII effectively reduced blood loss andreduced the time to achieve adequate hemostasis more than fibrin alone or thrombin-

coated gelatin sponges.[113]

Consultations

A hematologist, orthopedist, physical therapist, dentist, social worker, psychologist, infectious

disease specialist, gastroenterologist/hepatologist, geneticist, and an appropriately equippedspecial laboratory all play important roles in providing optimal care for patients with FXIII

deficiency and their families.

The efforts of theNational Hemophilia Foundationand its regional chapters must be recognized

in helping to educate patients, assist service providers, foster dialog regarding problems andsolutions among patients with bleeding disorders, and improve conditions for the entirecommunity through support of legislation.

Diet

A healthy and nutritional diet should be encouraged.
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Activity

Appropriate physical activity and physical therapy must be encouraged to maintain and preserve

muscle function.

Medication Summary

For FXIII replacement therapy, 2 intermediate-purity FXIII concentrates are being tested or are

commercially available for use. FFP and cryoprecipitate also are used. An FFP dose of 2-3

mL/kg every 4 weeks has been used for replacement therapy under steady-state conditions.Dosing of cryoprecipitate is empiric, since no standardized amount of FXIII exists for

cryoprecipitate. Repeat dosing should be guided by the adequacy of a prior dose as determined

by FXIII assays. FXIII concentrate, human (Corifact) is commercially available in the United

States. In December 2013, a recombinant FXIII A-subunit product (Tretten) was approved forpreventing bleeding episodes in patients with congenital FXIII-a subunit deficiency.

[114]

PLAS+SD is ABO blood type specific. As a result of treatment with 1% tri(n-butyl)phosphate(or TNBP as the solvent) and 1% Triton X-100 (as the detergent), lipid-enveloped viruses (eg,

HIV, HBV, HCV, Hantavirus, Marburg virus, Ebola virus) are disrupted and killed in significant

numbers. The resulting fragments are inactive and cannot replicate or cause disease. PLAS+SDhas proven efficacy in treating coagulation factor deficiencies when factor concentrate isunavailable. SD-treated plasma offers more protection to patients than is found in standard FFP.

Patients with FXIII deficiency have been specifically treated successfully with PLAS+SD.

Information regarding PLAS+SD can be found in the manufacturer's product circular.[115]

Traditionally, FFP has been the source of factors for the treatment of coagulation factor

deficiencies for which no concentrates are available; FXIII deficiency falls into this category.

Higher risks of virally transmitted illnesses remain among patients who are recipients of multipleunits of FFP. The greater degree of viral safety assured by this treatment has led to the exclusive

use of PLAS+SD instead of FFP in some countries (Norway and Belgium).

PLAS+SD delivers consistent and reproducible levels of coagulation factors. In contrast to the

extreme variability in FFP, PLAS+SD contains no leukocytes, and physiologic inhibitor levels

are mostly within reference range, with the exception of a moderate reduction in the levels of a2

PI (approximately 0.48 IU/mL) and protein S (approximately 0.52 IU/mL). In addition,coagulation zymogens are not activated, reference range levels of other plasma proteins and

immunoglobulins are present, and all lots have anti-HAV antibody levels greater than 0.8 IU/mL,

providing passive administration of antibody that may neutralize HAV. PLAS+SD also lacks the

largest vWF multimers and has proven efficacy in the treatment of a variety of bleedingdisorders.

Disadvantages of PLAS+SD use include minor allergic reactions as observed with other blood

products but that respond to antihistamines. PLAS+SD is contraindicated in patients with known

IgA deficiency.


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FXIII levels and efficacy of PLAS+SD: FXIII levels in 3 representative lots of pooled plasma

(starting material prior to SD and other treatments) were 1.18 0.05 U/mL (average standard

deviation), with levels of 1.23 0.06 U/mL in the final SD-treated, ultrafiltered, and sterile-filtered product.

Four patients with an inherited FXIII deficiency received successful prophylaxis with 1-2 U ofPLAS+SD administered every 21-40 days on a total of 39 occasions over 42 months (range in

each patient, 2-15 mo). PLAS+SD was proven to be equivalent to FFP in preventing

hemorrhages in patients with known FXIII deficiency. A fifth patient with FXIII deficiency wastreated successfully for soft tissue hemorrhages on an on-demand basis.

[116]

When PLAS+SD was stored at -18C, FXIII activity was 1.14 0.09 U/mL at the start and 1.33 0.05 U/mL after 18 months of storage. Currently, based on additional data submitted,

PLAS+SD has a US Food and Drug Administration (FDA)-approved 2-year shelf life according

to F. Darr, MD, of the American Red Cross (Fred Darr, MD, e-mail, February 2002). Therefore,

evidence exists that FXIII activity remains stable during long-term storage.

All PLAS+SD units that are administered should be ABO compatible with each patient's red

cells. Adverse reactions include minor allergic reactions and volume overload. Rarely, citratetoxicity, hypothermia, and other metabolic problems arise if large volumes are used rapidly.

Noncardiogenic pulmonary edema can occur. Antibody-induced positive results to the direct

antiglobulin test and hemolysis also may occur rarely.[116]

See the drug tables below for further details on the use of PLAS+SD instead of FFP.

Careful screening of blood donors and viral testing of donated blood (HBV surface antigen,

antibody to HBV core antigen, HCV, antibody to HIV-1 and HIV-2, HIV p24 antigen, antibodies

to human T-cell leukemia virus [HTLV] types I and II, and screening for elevated levels ofalanine aminotransferase [ALT]) have improved safety of blood products, but risks remain for a

variety of reasons including failure to detect infections during the "window" or incubation period

before currently available test results become positive.

Other types of infections in which screening currently is not performed, tests are not available, or

the presence of infection is unknown continue to cause concerns. Some of the emergingpathogens previously referred to include HIV-2, HIV type O, hepatitis G, TTV, human

herpesvirus 8, the SEN family of viruses, and prions causing Creutzfeldt Jacob disease [CJD]

and nvCJD.[117, 118, 119]

Newer emerging technologies, such as those using nucleic acid chemistry, are being used to

inactivate viruses, bacteria, and parasites and to attempt to remove prions, thus making blood and

blood components safer than they are currently. These newer technologies attempt to preserveclinically useful components of blood while improving its safety. Potentially, these

methodologies could be used to improve the safety of a wide variety of products.

Adjunctive role of inhibitors of fibrinolysis: Recognition of the importance of the lysine-binding

sites in various interactions in the fibrinolytic pathway led to the synthesis of lysine analogs such


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as EACA and AMCA. These synthetic lysine analogs induce a conformational change in

plasminogen when they bind to its lysine-binding site; plasminogen has the shape of a prolate

ellipsoid after EACA binds to it. The bound plasminogen-EACA elongates into a long structurein which the interaction between the parts of plasminogen, as they existed, are lost. In vivo, the

structures probably prevent plasminogen activation and, in large doses, bind plasmin, thereby

preventing it from binding to its substrate fibrin. In the plasminogen-EACA binding sites, thetightest binding is to kringle 1 followed by kringles 4 and 5. The interaction with kringle 2 isweak, and kringle 3 does not interact at a

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