Antibody Testing in Myopathies

AANEM Annual MeetingOctober 2021

Payam Soltanzadeh, MDAssociate Clinical Professor of Neurology

UCLA Neuromuscular Program

Conflicts of Interest

No conflicts of interest related to this talk

Received research funding from RA Pharmaceuticals (now acquired by UCB) to study a product for immune mediated necrotizing myopathies (IMNM).

Dermatomyositis (DM)- Weakness over weeks to months

- Symmetric and usually more involvement of the proximal muscles

- Axial muscles can also be involved

- Spares facial and eye muscles

- Skin lesions (heliotrope rash, Gottron papules)

- In some forms, lung is involved leading to interstitial lung disease (ILD)

- Soft tissue (subcutaneous) involvement in some forms

- CK elevation to various degrees but can be normal

Polyomyositis (PM): No skin involvement

Dermatomyositis pathology: microangiopathy starting from endothelial cells, mediated by the complement (deposition of the C5b-9 membrane attack complex on endothelial cells). Ischemia/infarction with inflammation (CD4+ lymphocytes)

neuromuscular.wustl.edu

Patterns of EMG abnormalities in myopathies:nonspecific

• Myopathic MUPs with fibrillation potentials (irritable myopathy)

• Myopathic MUPs without fibrillation potentials

• Prominent myotonic discharges

• Normal EMG

Timeline of the Discovery of Myositis Specific autoantibodies (MSA’s)

McHugh and Tansley. Nature 2018; 14: 290

Myositis Specific Antibodies (MSAs):

Highly specific to myositis syndromes

MSA have a low sensitivity but collectively their sensitivity may reach 60–70%

Help with diagnosis, treatment and prognosis

Myositis-Associated Antibodies (MAAs)

Not specific and can be seen in other autoimmune conditions

Myositis Associated Autoantibodies (MAA) can be found in patients with overlap syndromes such as scleroderma and lupus. MAA can also be found in non-overlap syndromes.

Myositis-Specific Autoantibodiesparticular antibodies may indicate a distinctive clinical pictures with

therapeutic and prognostic significance

• Immune-mediated necrotizingMyopathy (IMNM)– Anti-signal recognitionparticle (SRP)– Anti-HMG-CoAreductase (HMGCR) 3-Hydroxy-3-methylglutaryl-coenzyme A Reductase - Anti-mitochondrial myositis– Antibody negativeIMNM

• Dermatomyositis– Anti-p155/TIF1g– Anti-MDA5– Anti-Mi2– Anti-NXP-2– Antibody negative DM

• Antisynthetase syndrome– Anti-Jo-1, -PL7, -PL12,

Modern classification of autoimmune and/or inflammatory myopathies

1. Dermatomyositis (DM)

2. Anti-synthetase syndrome (ASyS)

3. Immune mediated necrotizing myopathies (IMNM): anti-SRP, anti-HMGCR,

anti-mitochondrial M2 antibody (AM2A)

4. Sporadic inclusion body myositis (sIBM)

5. Overlap myositis: when with another well-defined connective tissue disease

like scleroderma, Sjogren, SLE, or RA

6. Others:

- Myositis in GVHD

- Myositis in patients treated with checkpoint inhibitors

”polymyositis (PM)” is now being abandoned/discouraged term

Betteridge & McHugh. Journal of Internal Medicine, 2016, 280; 8–23

Myositis autoantibodies and their key clinical associations

Anti-Mi-2 (classic DM): acute onset, severe rash, higher CK, and good response to therapy.

Anti-MDA5 (melanoma differentiation associated protein 5): ulcerating skin lesions; often with severe and rapidly progressive interstitial lung disease (ILD) and HIGH MORTALITY, particularly in Eastern Asian populations; Needs aggressive multidisciplinary treatment. Can be Amyopathic

TIF1-gamma (transcriptional intermediary factor 1-gamma [Anti-p155 ]) > adult cancer-associated dermatomyositis with 89% specificity and >50% sensitivity: subcutaneous edema, calcinosis and dysphagia are more common than other DM’s

DM and cancer (usually >40 yo; most within the first 3 years of diagnosis of DM): More than 50% of adults will develop cancer. Not a particular cancer type. ovary > pancreas > stomach > intestinal > lymphoma

Anti-NXP2 (nuclear matrix protein 2): Mostly in Juvenile DM (15% of juvenile DM) associated with subcutaneous edema and calcinosis. Muscle disease is generally severe at onset. Very rare in adult-onset DM so association with cancer not well established.

Anti-SAE (Small ubiquitin-like modifier Activating Enzyme): classic DM rashes with pathology not well characterized. Myositis is typically absent initially and develops later. Dysphagia more common.

Antibody based classification of Dermatomyositis (DM)

Heliotrope rash

http://www.dermnetnz.org

Gottron’s papules

Anti-Mi-2 (a transcription regulator and a component of the nucleosome remodeling deacetylase (NuRD) complex)Classic DMAcute onset, severe rash, muscle weakness is generally mild, CK can be very high, no other organs involved other than skin and muscle; Good response to therapy

Anti-MDA5 (melanoma differentiation associated protein 5): First identified as CADM-140 Ab, cytoplasmic RNA-specific helicase, belongs to a family of retinoic acid-inducible gene (RIG)I-like receptors

More in Asia and Africa (10-48% of DM patients)

Bilateral ground glass opacities

Ulcerating skin lesions (photo by Dr Benveniste in France)

Calcinosis: more in juvenile DM and significant association with NXP2 Ab

https://musculoskeletalkey.com/juvenile-dermatomyositis/

Valenzuela et al. JAMA Dermatol. 2014 Jul;150(7):724-9

Anti-synthetase syndrome (anti-Jo1 and others)

Anti-ARS antibodies Auto-antigen Clinical features

Anti-Jo1 histidyl Most common

Anti-PL7 theronyl More Severe ILD than Jo-1

Anti-PL12 alanyl More Severe ILD than Jo-1

Anti-OJ isoleucyl

Anti-EJ glycyl

Anti-KS asparaginyl

Anti-Zo phenylalanyl

Anti-SC lysyl

Anti-JS glutaminyl

Anti-YRS tyrosyl

Anti-synthetase syndrome is a rare autoimmune disease characterized mainly by interstitial lung disease (ILD), myositis, and arthritis reportedly in 90% of cases.

Other manifestations: fever, rashes, and Raynaud’s syndrome have also been seen less commonly.

Ab’s against aminoacyl-t-RNA-synthetases

Anti-synthetase syndrome

ILDMechanic’s hand

At least 50% of patients with inflammatory myopathy and ILD (interstitial lung

disease) have anti-Jo-1 antibodies

Anti-Jo-1 responds better to Tx.

No association with cancer

May respond better to rituximab (Andersson, et al. Rheumatology, 2015; 54: 1420)

Common Myositis-Associated Antibodies (MSAs)

McHugh and Tansley. Nature 2018; 14: 290

Immune Mediated Necrotizing Myopathies (IMNM)

Muscle fiber necrosis and regeneration and little or no inflammation

Not considered “inflammatory myopathy” or “myositis” in pure sense. CK always above 1000 and usually higher than DM. Can lead to severe atrophy.

1) anti-signal recognition particle (SRP)- Severe acute onset myositis, dilated cardiomyopathy is a possibility- High CK level (> 10 000), poor response to therapy; needs aggressive Tx- Difficult to treat; Cardiomyopathy and ILD in some patients

2) Statin-triggered anti-HMG-CoA reductase antibodies (also called statin-associated necrotizing autoimmune myopathy (SANAM))- Highly sensitive and specific ab (>99%)- Wide clinical spectrum, Milder in the elderly. Usually slower than anti-SRP - Minimal or no extra-muscular features

3) Anti-mitochondrial M2 antibody (AM2A). Can be with primary biliary cirrhosis- Myositis plus significant cardiac involvement

4) IMNM without a known antibody. Can be associated with cancer

Different manifestations of statin myopathies1. hyperCKemia (sometimes asymptomatic)

2. Myalgia

3. Self-limited necrotizing myopathy +/- rhabdomyolysis (CK > x10 times upper limit of normal)

4. Immune-mediated necrotizing myopathy +/- rhabdomyolysis (with anti-HMG-CoA antibodies).

-Can occur in children and patients without exposure to statins “statin naïve” (statin-like compounds like red yeast rice)

-More severe in children and younger adults, more benign in the elderly

- Can be at times paraneoplastic. Several malignant tumors, including esophageal squamous cell carcinoma overexpress HMGCR protein

- IVIg is the treatment of choice

Inclusion body myositis (IBM)

Most common acquired myopathy > 50 yo Progression over decades Described first in “refractory polymyositis” or stable “ALS” patients Forearm flexors and quadriceps; 20-40% dysphagia (usually mild) Characterized by certain pathological features including rimmed vacuoles

IBM muscle pathology

http://neuropathology-web.org/chapter13

http://www.intechopen.com

cN1A is an enzyme catalyzing the conversion of adenosine monophosphate (AMP) into adenosine and phosphate.Antibodies against cytosolic 5’-nucleotidase 1A (cN1A) )[NOT IN MYOSITIS PANELS] have been detected in up to about 50% of IBM patients. Can also be found in lupus and Sjogren syndrome. ?MAA rather than an MSA.

Sensitivity of 34% to 70% and a specificity of higher than 90% for sIBM. Clinical utility/value of cN1A antibody has yet to be clarified. If clinical features fit, the presence of this ab can be diagnostically helpful.

There may be a relationship between anti-cN1A and higher disease severity- Goyal et al. J Neurol Neurosurg Psychiatry. (2016) 87:373–8- Lilleker et al. Ann Rheum Dis. 2017 May;76(5):862-868

One recent study indicated lack of correlation between the severity of IBM and presence of cN1A antibody.

- Paul P, et al. Muscle Nerve. 2021 Apr;63(4):490-496.

IBM•. 2017 May;76(5):862-868

Limitations of Muscle Biopsy• Only 60% of DM cases have perifascicular atrophy

• Can’t easily distinguish DM from anti-synthetase syndrome

• Can’t distinguish Mi2 vs. TIF1g vs. NXP2 vs. MDA5

• Can’t distinguish anti-SRP vs. anti-HMGCR

• Only 80% of IBM patients have rimmed vacuoles

• Genetic myopathies can have prominent inflammatory changes on

biopsy: Dystrophinopathies (+MHC-I expression), Limb-girdle muscular

dystrophy (LGMD)-2B (dysferlinopathy) (+MHC-I expression),

Facioscapulohumeral muscular dystrophy (FSHD) (without MHC-I expression)

Classification of idiopathic inflammatory myopathies in 260 patients based on 708 variables per patient such as cancer, lung involvement, and myositis-specific antibodies (Mariampillai from Benveniste group.

JAMA Neurol. 2018;75:1528)

Most cases previously diagnosed as polymyositis (PM) are now reclassified as:

IBM (inclusion body myositis)IMNM (immune mediated necrotizing myopathy)Anti-synthetase syndrome without a rashMyositis-overlap (e.g., scleroderma myositis)orgenetic muscle disease (muscular dystrophies)

Remaining myopathies with inflammation in muscles without features of other myositis syndromes may be called “myositis”

How about the term “polymyositis”?

MyoMarker Panels: Most do not include HMGCR or cN1A antibodies

Oklahoma Medical Research Foundation (OMRF): Comprehensive Myositis Autoantibody ProfileJo-1, PL7, PL12, EJ, OJ, SRP, Mi-2, PMScl, Ku, Ro60, U1RNP, U2RNP, p155/140 (TIF1g), MJ (NXP2), caDM140 (MDA5)

RDL’s MyoMarker 3 Plus: Jo-1, Mi-2, PL-12, PL-7, EJ, OJ, SRP, Ku, U2 snRNP, PM/Scl, MDA5, NXP2, TIF-1γ, SSA 52 kD, IgG, U1 RNP, Fibrillarin U3 RNP

ARUP’s Extended Myositis (including HMGCR) Panel Preferred lab by UCLA Pathology

MayoClinicMyoMarker 3 panel

Washington University Neuromuscular Lab:Myopathy 2 panel

Some key clinical points in immune mediated/inflammatory myopathies

- EMG and muscle biopsy findings can be nonspecific

- Order myositis antibody panels early (before giving IVIg)

- If CK is very high (few thousands) suspect IMNM

- If CK is very high (few thousands) with history of statin use, consider HMGCR

- If there is ILD, consider anti-synthetase syndrome or MDA-5

- skin changes may or may not be present in DM or anti-synthetase syndrome

- In TIF1-gamma (and maybe NXP2) positive adult DM, look hard for cancer in the first 3 years. HMCGR ab+ and seronegative IMNM’s can also be associated with cancer.

- If there are classic clinical features of IBM and positive cN1a ab, it is most likely IBM and this will not respond to current immunotherapies

Take home messages

In the appropriate clinical context, myositis specific antibodies (MSAs) such as HMGCR, SRP,

MDA-5, Jo-1 and TIF-1γ can significantly help with the diagnosis, prognosis and management of

patients with immune mediated or inflammatory myopathies; and at times, obviate the need for

muscle biopsy.

Thank you!