Myositis Antibodies

Simply Put

A diagnosis of idiopathic inflammatory myopathy (IIM), or myositis, can be made through various methods including a clinical exam, thorough patient history, blood work, EMG, MRI, and often, a muscle or skin biopsy. When IIM is part of the differential diagnosis, Myositis-Specific Antibodies (MSA) should also be a part of the testing.

As the name suggests, the MSAs are specific to myositis. A physician can order the blood work for the MSA panel, however, if immune-mediated necrotizing myopathy (IMNM) is suspected the anti-HMGCR antibody must be ordered separately as it is not currently a part of the MSA panel.

Specific antibodies for Myositis patients

Myositis-Specific and Myositis-Associated Antibodies

High-level overview of Myositis-Specific Autoantibodies

Studies have shown many myositis-specific autoantibodies (MSAs) that can be useful for the diagnoses as well as classification of idiopathic inflammatory myopathies (IIM) because they have been shown to correlate with distinct clinical phenotypes.

Anti-Jo-1, anti-PL-7, anti-PL-12, anti-EJ, anti-KS, anti-OJ, anti-Ha, and anti-Zo antibodies target aminoacyl-tRNA synthetases and represent anti-synthetase syndrome. Anti-synthetase syndrome is characterized by myositis, interstitial lung disease, arthritis, fever, Raynaud’s phenomenon, and mechanic’s hands.

Anti-Mi-2, anti-MDA5 (anti-CADM140), anti-TIF1 (anti-155/140, anti-p155), anti-NXP-2 (anti-MJ), and anti-SAE antibodies are specific for dermatomyositis. In particular, anti-MDA5 antibodies are clinically associated with amyopathic dermatomyositis developing into rapidly progressive interstitial lung disease, whereas anti-TIF1 and anti-NXP-2 antibodies are closely correlated with cancer-associated dermatomyositis in adults. In addition, anti-TIF1 and anti-NXP-2 antibodies are predominant MSAs found in juvenile dermatomyositis, and the latter was correlated with a high incidence of calcinosis. Furthermore, anti-SRP and anti-3-hydroxy-3-methylglutaryl-coenzyme A (anti-HMG-CoA) antibodies have been found in patients with immune-mediatd necrotizing myopathy (IMNM).

A recent study suggested the presence of autoantibodies to a 43-kDa muscle protein in patients with inclusion body myositis.

Although the pathogenic role of MSAs remains unknown, recent studies have shown that myositis autoantigens are expressed at high levels in regenerating muscle fibers, which may initiate or amplify autoimmune responses in iIIM.

Glossary of terms for autoantibody listing:

Below are abbreveiations used when discussing the autoantibodies.

  • AS – Antisynthetase Syndrome
  • PM – Polymyositis
  • DM – Dermatomyositis
  • JDM – Juvenile Dermatomyositis
  • IBM – Inclusion Body Myositis
  • IMNM – Immune-Mediated Necrotizing Myopathy
  • ILD – Interstitial Lung Disease
  • CAM – Cancer-Associated Myositis
  • MCTD – Mixed Connective Tissue Disease

  • RP – Raynaud’s Phenomenon
  • SLE – Systemic Lupus Erythematosus
  • Myositis* – May be PM or DM
  • SS-A – Sjogren’s syndrome A
  • SSc – Systemic Sclerosis or Scleroderma
  • MDA5 – Melanoma differentiation-associated gene 5
  • > – more often than

Myositis-Specific Antibodies (MSA)

MSAs can assist your doctor in helping to confirm a diagnosis of certain types of myositis such as polymyositis and dermatomyositis. They are also helpful in diagnosing Antisynthetase syndrome. These antibodies also offer some insight into potential complications you may experience during the course of your disease and potential treatment options that may work best.

It is estimated that 50% of patients with polymyositis or dermatomyositis have myositis-specific antibodies, so when a clinical exam and other testing suggest the possibility of myositis, the presence of these antibodies can be supporting evidence for a diagnosis. Myositis-specific antibodies have also improved our understanding of myositis by leading to the identification of certain clinical patterns.

Antisynthetase autoantibodies

Anti-Jo1 (Histidyl-tRNA synthetase)

  • PM, DM + ILD; Arthritis (75%), Raynaud’s Phenomenon (50%), Mechanics Hands (20%)
  • Seasonal Onset Potentially: Spring

Anti-PL-7 (Threonly-tRNA synthetase)

  • PM, DM + ILD; infrequent muscle involvement, severe arthritis

Anti-PL-12 (Alanyl-tRNA synthetase)

  • ILD more often than myositis, pulmonary hypertension, esophageal involvement

Anti-EJ (Glycyl-tRNA synthetase)

  • PM more often than DM + ILD

Anti-OJ (Isoleucyl-tRNA)

  • ILD + PM/DM

Anti-KS (Asparaginyl-Transfer RNA Synthetase)

  • ILD more often than myositis*

Anti-Zo (Phenylalanyl-tRNA synthetase)

  • ILD + myositis*

Anti-Ha (Tyrosyl-tRNA synthetase)

  • ILD + myositis*

Non-synthetase Autoantibodies

Anti-SRP (SRP – signal recognition particle)

  • Severe, acute, and resistant immune-mediated necrotizing myopathy.
  • One of two known autoantibodies to diagnose IMNM.
  • Anti-SRP Myopathy: Severe weakness and functional disability
  • Seasonal onset shown in studies: August and January
  • Highly elevated CK levels. Often resistant to available off-label medications.

Anti-Mi-2 (DNA helicase)

  • DM with rash more often than muscle symptoms (clinically amyopathic dermatomyositis)
  • Muscle biopsy may show prominent necrosis.
  • See citation below for the clinical phenotype of dermatomyositis (DM) with anti-Mi2 autoantibodies.

Anti-HMGCR (anti 200/100)

  • One of two known autoantibodies to diagnose IMNM.
  • It can be statin-associated but even those who have never taken statin drugs may test positive.
  • Anti-HMGCR Myopathy: Severe muscle weakness, highly elevated CK levels. Often resistant to available off-label medications.

Anti-MDA5 (anti-CADM 140)

  • DM: CAM, DM with rapidly progressing lung disease

Anti-TIF1-y  (Anti-155/140)

  • CAM in adults
  • JDM

Anti-SAE (Anti-Sumo)

  • DM: CAM, DM with rapidly progressing lung disease

More about Anti-Mi2 – Based on 2019 longitudual cohort study, those with anti-Mi2-positive DM have more severe muscle disease than patients with anti-Mi2-negative DM or patients with AS. Anti-Mi2 autoantibody levels correlate with disease severity and may normalize in patients who enter remission.Muscle biopsy shows prominent necrosis.

Iago Pinal-FernandezChristopher A. MecoliMaria Casal-DominguezKatherine PakYuji HosonoJulio HuapayaWilson HuangJemima AlbaydaEleni TiniakouJulie J. PaikCheilonda JohnsonSonye K. DanoffAndrea M. CorseLisa Christopher-StineAndrew L. Mammen

Myositis-Associated Autoantibodies (MAA)

Below is a listing of some of the known Myositis-Associated Antibodies (MAA). These can be found in those with myositis as well as with other autoimmune diseases such as Lupus, Scleroderma, and overlapping conditions with myositis. As more research is completed and released we will know and share more.

  • Anti-PM-Scl
    • PM or DM with SSc Overlap
  • Anti-U1-RNP
    • MCTD, overlap syndrome
    •  Can also be detected in patients with SSc or SLE
    • See citation below for the myositis clinical phenotype information.
  • Anti‐U5 snRNP
    • PM/SSc or SSc overlap
  • Anti-Ku
    • Myositis* / SSc / SLE overlap
  • Anti-Ro (SS-A) includes Ro60, Ro52
    • Myositis often with SS or SLE, may be associated with ILD (Ro52 especially)
  • Anti-56 kDa
    • Myositis, often with Jo-1

More about Anti-U1RNP – anti-U1-ribonucleoprotein (RNP) autoantibodies. Based on 2018 longitudual cohort study, patients with anti-U1-RNP myositis typically present with proximal weakness and necrotizing muscle biopsies. Arthritis, dermatitis, and ILD are the most common extramuscular clinical features. Pericarditis and glomerulonephritis are uniquely found in patients with anti-U1-RNP–positive myositis.

Maria Casal-DominguezIago Pinal-FernandezAndrea M. CorseJulie PaikJemima AlbaydaLivia Casciola-RosenCheilonda JohnsonSonye K. DanoffLisa Christopher-StineEleni TiniakouAndrew L. Mammen
  • Anti-KJ
    • PM, ILD, RP
  • Anti-Fer
    • Myositis
  • Anti-Mas
    • Myositis, rhabdomyolysis, chronic hepatitis
  • Anti-NXP-2 (Anti-MJ)
    • JDM: Severe muscle atrophy, functional impairment, and calcinosis.
    • Adult DM: Associated with dysphagia and soft tissue/peripheral edema
    • High cancer association
  • hPM51 (protein related to DNA repair)
    • Myositis

Other Myositis related antibodies

  • Anti-AMA
    • Anti-mitochondrial antibodies, may have cardiac involvement
  • Anti-NT5C1A
    • Inclusion Body Myositis

AMA Associated Myositis, Cardiac Involvement

Patients with inflammatory myopathy associated with antimitochondrial M2 antibodies (AMA) may have cardiac involvement, dropped head, and muscle atrophy. These antibodies bind to a protein in the mitochondria, the energy-producing factory of the cell. This may also be called “AMA-associated myositis.”

Heart disease may appear in the form of myocarditis (inflammation of the heart), severe arrhythmias, or cardiomyopathy (enlargement of the heart). Although the heart disease was often not recognized to be related to the myositis, treatments that suppressed the immune system led to improvements in these symptoms.

Anti-mitochondrial antibodies identify a distinct inflammatory myopathy phenotype that is frequently associated with chronic skeletal muscle disease and severe cardiac involvement. Diagnosing this early is essential for treatment.

Inclusion Body Myositis Antibodies

It has been recently discovered that some inclusion body myositis (IBM) patients may have antibodies that can help in making a correct diagnosis, along with additional testing. These antibodies are anti-cytosolic 5’ –nucleotidase 1A  (anti-CN1A or anti-NT5C1A).

This autoantibody is positive in about one-half of IBM patients. A negative test does not mean a patient does not have IBM, however, a positive test makes it likely that inclusion body myositis is the correct diagnosis.

Polymyositis and Inclusion Body Myositis can appear much the same, especially at first. The NT5C1A antibody test can now help to distinguish the two as this antibody is rarely positive for those with polymyositis.

This antibody test is sometimes positive for other autoimmune diseases and is not stricly specific to IBM.

Autoantibodies for Myositis are currently undergoing more research:

Disclaimer: Research is ongoing on many of the autoantibodies listed on this page. Please note that as research continues and new evidence is found, we will try to keep this page updated. This is for informational purposes only based on information we have at the time of this writing.

Simply Put

“Simply Put” is a service of Myositis Support and Understanding, to provide overviews of Myositis-related medical and scientific information in understandable language.

MSU volunteers, who have no medical background, read and analyze often-complicated medical information and present it in more simplified terms so that readers have a starting point for further investigation and consultation with healthcare providers. The information provided is not meant to be medical advice of any type.

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