Acquired Hemolytic Anemias (2)

8/6/2019 Acquired Hemolytic Anemias (2)

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ACQUIRED HEMOLYTIC ANEMIASACQUIRED HEMOLYTIC ANEMIAS

BY

Dr.Ammar


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Acquired haemolytic anaemiasAcquired haemolytic anaemias

Divided into two main categories

depending on the mechanism by which

the premature destruction of red bloodcells is produced.

Immune haemolytic anaemias

Non-immune haemolytic

anaemias


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IMMUNE HEMOLYTIC ANEMIAIMMUNE HEMOLYTIC ANEMIA

Antibody-mediated haemolysis is an

important cause of acquired haemolytic

anaemia. Antibodies may be:

autoantibodies

alloantibodies.


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IMMUNE HEMOLYTIC ANEMIAIMMUNE HEMOLYTIC ANEMIAGENERAL PRINCIPLESGENERAL PRINCIPLES

All require antigen-antibody reactions

Types of reactions dependent on:

Class of Antibody

Number & Spacing of antigenic sites on cell

Availability of complement

Environmental Temperature

Functional status of reticuloendothelial system

Manifestations Intravascular hemolysis

Extravascular hemolysis


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Classification of hemolytic anemias


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Autoimmune Hemolytic AnemiasAutoimmune Hemolytic Anemias

These are caused by antibody production

by the body against its own red cells.

Warm and cold types according towhether the antibody reacts more strongly

with red cells at 37C or 4C.


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Warmautoimmune haemolyticanaemiasWarmautoimmune haemolyticanaemias

The red cells are coated with immunoglobulin(Ig)

(IgG) alone or with complement

They are taken up by RE macrophages which

have receptors for the Ig Fc fragment.

Part of the coated membrane is lost so the cell

becomes progressively more spherical to

maintain the same volume and is prematurelydestroyed in the spleen.


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Clinical featuresClinical features

Any age

Either sex

presents as a haemolytic anaemia of varying severity

The spleen is often enlarged.

It may occur alone or in association with other diseases

May arise in some patients as a result of methyldopatherapy

When associated with idiopathic thrombocytopenicpurpura (ITP)it is known as Evans' syndrome

When secondary to systemic lupus erythematosus thecells typically are coated with immunoglobulin andcomplement.


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Lab findingsLab findings

Positive DAT

Normocytic normochromic anemia

Increased reticulocytosis Spherocytosis

Presence of autoantibodies in serum

Leukocyte counts are normal Platelet count normal or slightly decreased


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Coombs test(direct):Coombs test(direct):

Looks for immunoglobulin &/or complement of

surface of red blood cell (normally neither found

on RBC surface)

Coombs reagent - combination of anti-humanimmunoglobulin & anti-human complement

Mixed with patients red cells; if immunoglobulin

or complement are on surface, Coombs reagentwill link cells together and cause agglutination of

RBCs


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Coombs test (indirect):Coombs test (indirect):

Looks for anti-red blood cell antibodies in the patientsserum, using a panel of red cells with known surfaceantigens

Combine patients serum with cells from a panel ofRBCs with known antigens

Add Coombs reagent to this mixture

If anti-RBC antigens are in serum, agglutination occurs


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TreatmentTreatment

1. Remove the underlying cause (e.g.methyldopa)

2. .Corticosteroids.(Prednisolone)

3. Splenectomy

4. Immunosupression(Azothioprim,Cyclophosphomide)

5. Monoclonal antibodies.Rituximab(anti-CD20).Campath-IH(anti-CD52)

6. Folic acid

7. Blood transfusion


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Cold autoimmune hemolytic anemiasCold autoimmune hemolytic anemias

Monoclonal

idiopathic cold haemagglutinin syndrome

lymphoproliferative disordersPolyclonal

e.g. infectious mononucleosis

Mycoplasmapneumonia

attaches to red cells mainly in the peripheral

circulation where the blood temperature is cooled


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The antibody is usually IgM

Binds to red cells best at 4C.

IgM antibodies are highly efficient at fixingcomplement

Intravascular and extravascular

haemolysis can occur.


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Chronic haemolytic anaemia aggravatedby the cold

Intravascular haemolysis.

Mild jaundice

Splenomegaly

Acrocyanosis (pllrplish skin discoloration)

at the tip of the nose, ears, fingers andtoes caused by the agglutination of redcells in small vessels.


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Lab findingsLab findings

DAT positive with polyspecific AHG

Negative with anti-IgG

Positive with anti-C3 Cold agglutinin titre >1000 at 4oc

Normocytic normochromic anemia

Reticulocytosis Spherocytosis

Agglutinated RBCs


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Cold autoimmune hemolytic anemia


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TreatmentTreatment

keeping the patient warm

treating the underlying cause,

Alkylating agents such as chlorambucil ishelpful in the chronic varieties.

Both anti-CD20(rituximab) and anti-CD52

(Campath-lH) havebeen used. .


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Proxysmal cold hemoglobinuriaProxysmal cold hemoglobinuria

Acute intravascular hemolysis after exposure to

the cold.

It is caused by the Donath-Landsteiner

antibody, an IgG antibody with specificity for theP blood group antigens which binds to red cells

in cold but cause lysis in warm conditions.

viral infections,syphilis are predesposing factors.


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Alloimmune Hemolytic anemiaAlloimmune Hemolytic anemia

Hemolytic anemia of newborn

Hemolytic transfusion reaction

Allograft asoociated


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Hemolytic transfusion ReactionHemolytic transfusion Reaction

Caused by recognition of foreign antigens ontransfused blood cells

Several types

Immediate Intravascular Hemolysis (Minutes)

- Due to preformed antibodies; life-threatening Slow extravascular hemolysis (Days) -

Usually due to repeat exposure to a foreignantigen to which there was a previous

exposure; usually only mild symptoms Delayed sensitization - (Weeks) - Usually due

to first exposure to foreign antigen;asymptomatic


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PrePre--transfusion tests:transfusion tests:

ABO & Rh Type of both donor & recipient

Antibody Screen of Donor & Recipient,including indirect Coombs

Major cross-match by same procedure(recipient serum & donor red cells)


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Hemolytic anemia of the newborn:Hemolytic anemia of the newborn:

Due to incompatibility between mother negative for anantigen & fetus/father positive for that antigen.

Usually occurs with 2nd or later pregnancies.Requiresmaternal IgG antibodies vs. RBC antigens in fetus

Can cause severe anemia in fetus, with erythroblastosisand heart failure

Hyperbilirubinemia can lead to severe brain damage

(kernicterus) if not promptly treated

HDN due to Rh incompatibility can be almost totallyprevented by administration of anti-Rh D to Rh negativemothers after each pregnancy


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Drug induced hemolyticDrug induced hemolytic

anemias:anemias:1. Antibody directed against drug-red cellmembrane complex.e.g penicillin

2. Deposition of complement via drugprotein(antigen)-antibody complex on the

RBC e.g quinidine, rifampicin.

3. True autoimmune hemolytic anemia e.g

methyl dopa, pencillin(high doses).


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II) NonII) Non--ImmuneHemolytic anemiasImmuneHemolytic anemias

Due to mechanisms or agents other thanantibodies +/or complement e.g:

Mechanical (traumatic)(fragmentaion)

Toxins

Infections

Splenomegaly

Burn(physical)

Renal and liver failure

chemical


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MechanicalMechanical

(traumatic,Fragmentation)(traumatic,Fragmentation)

Due to direct trauma(stress)to the RBCcausing fragmentation and intra-vascularhemolysis.

Peripheral blood smears : schistocytes Cause:

1.Physical damage to RBC by abnormalsurfaces;

Prosthetic valves

Patches

Valvular diseasee.g stenosis

2.AV malformations


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Microangiopathic hemolysis:

Due to contact btw RBC & abnormal intima of

vessels.

Examples:

DICMalignant hypertension

Disseminated malignancies

TTPHUS

Vasculitis e.g polyarteritis nodosa

Pre-eclampsia/HELLP syndrome


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Paroxysmal nocturnalParoxysmal nocturnal

haemoglobinuria(PNH)haemoglobinuria(PNH)

Rare, acquired, clonal disorder of marrow stem

cells in which there is deficient synthesis of the

glycosylphosphatidylinositol .(GPI)

mutations in the X chromosome gene coding forphosphatidylinositol glycan protein A (PIG-A)

GPI-linked proteins (such as CD55 and CD59)

are absent from the cell surface of all the cells

derived from the abnormal stem cell leading to

lysis.


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Haemosiderinuria

Recurrent thromboses of large veins

including portal and hepatic veins intermittent abdominal pain brought about

by thrombosis of mesenteric veins

Aplastic anaemia


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DiagnosisDiagnosis

Flow cytometry

shows loss of expression of the CPI-

linked proteins,CD55 (DAF) and CD59(MIRL).

Ham's test.


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HAM TESTHAM TEST

Principle

The patient's red cells are exposed at

37C to the action of normal or thepatient's own serum suitably acidified to

the optimum pH for lysis (pH 6.5-7.0)


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MethodMethod

1. Deliver 0.5 ml samples of fresh normal seruminto 6 (3 pairs) tubes.

2. Place two tubes at 56C for 10-30 min toinactivate complement.

3.Keep the other 2 pairs of tubes at roomtemperature and add to the serum in 2 of thetubes one-tenth volumes (0.05 ml) of 0.2 mol/lHCl.

4.Add similar volumes of acid to the inactivatedserum samples

5. Place all the tubes in a 37C waterbath.


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Contd.Contd.

6. Wash samples of the patient's red cells and of controlnormal red cells (compatible with the normal serum) andprepare 50% suspensions in the saline.

7. Then add one-tenth volumes of each of these cell

suspensions (0.05 ml) to one of the tubes containingunacidified fresh serum, acidified fresh serum, andacidified inactivated serum, respectively.

8.Mix the contents carefully and leave the tubes at 37C.

9. Centrifuge them after about 1 hour.

10. Measure the lysis in a photoelectric colorimeter using ayellowgreen filter or in a spectrometer at a wavelengthof 540 nm.


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ResultsResults

If the test cells are from a patient with PNH, they

will undergo

Definite ,Incomplete lysis in the acidified serum.

Much less lysis, or even no lysis at all, will be

visible in the unacidified serum.

No lysis will be brought about by the acidified

inactivated serum. The normal control sample ofcells should not undergo lysis in any of the three

tubes.


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TreatmentTreatment

Eculizumab (anti-complement antibody)

Iron therapy

long-term anticoagulation with warfarin Immunosuppression

Allogeneic stem cell transplantation


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THANK YOUTHANK YOU

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Acquired Hemolytic Anemias (2)