Indication

Suspicion of polymyositis (PM), dermatomyositis (DM) or overlap syndrome

Sample material

Serum

Minim. volume: 0,5 mL

Transport

Within Sweden

room temperature

International

room temperature

Method

Immunoblot

Reference interval

Mi-2α, Mi-2β, Ku, SRP, Jo-1, PL-7, PL-12, EJ, OJ, PM-Scl75, PM-Scl100, NXP2, Ro52, och SAE1: ≤10 negative MDA5 och TIF1γ: ≤5 negative (6-10 borderline)

Result

Results are reported as negative, borderline, or positive with reaction intensity.

Interpretation

PL-12

Anti-PL-12 is a type of anti-synthetase antibody and can be detected in <5% of patients with inflammatory myositis. Anti-PL-12 is often (90%) associated with interstitial lung disease that may occur with or without myositis.

PL-7

Anti-PL-7 is a type of anti-synthetase antibody and can be detected in <5% of patients with inflammatory myositis. Anti-PL-7 is often associated with interstitial lung disease that may occur with or without myositis.

Ro52

Anti-Ro52 can often be detected in myositis with or without other myositis-associated antibodies and are associated with an increased risk of interstitial lung disease. Anti-Ro52 is also associated with several other autoimmune conditions such as rheumatic diseases and autoimmune liver disease.

Jo-1

Anti-Jo1 is the most common type of anti-synthetase antibodies and is detected in up to 20-30% of patients with inflammatory myositis. Interstitial lung disease is often also seen.

EJ

Anti-EJ are a type of anti-synthetase antibodies and can be detected in <5% of the patients with inflammatory myositis.

OJ

Anti-OJ are a type of anti-synthetase antibodies and can be detected in <5% of the patients with inflammatory myositis. Anti-OJ is strongly associated with interstitial lung disease.

Ku

Anti-Ku is associated with myositis that clinically overlaps with other rheumatic systemic diseases and can in some cases also be detected in SLE, Sjögren's syndrome, idiopathic pulmonary fibrosis and inflammatory myositis. Anti-Ku is often detected together with antibodies against SSA/Ro52.

PM-Scl75

Antibodies against the PM-Scl complex are associated with myositis that clinically overlaps with other rheumatic systemic diseases. The antibodies are usually associated with positive nucleolar ANA and are usually directed against the 75 kD and 100 kD subunits. Isolated occurrence of antibodies against PM-Scl75, i.e. without the presence of anti-PM-Scl100, has a significantly lower diagnostic value and can also be seen in healthy people.

PM-Scl100

Antibodies against the PM-Scl complex are associated with myositis that clinically overlap with other rheumatic systemic diseases and are often associated with Raynaud's phenomenon, arthritis, muscle involvement and effects on the skin and lungs. Usually, positive ANA with a nucleolar pattern is also seen. The antibodies are usually directed against the subunits 75 kD and 100 kD.

SRP

Anti-SRP is a strong marker for severe and rapidly progressing necrotizing myositis that often responds poorly to treatment. Cardiac involvement may occur. The level of anti-SRP levels correlates to disease activity. Dysphagia may occur. Anti-SRPs are rarely associated with interstitial lung disease or malignancy.

Mi-2α and Mi-2β

Antibodies against Mi-2 are associated with classic dermatomyositis, which often has a mild course and responds well to treatment. Low risk of pulmonary involvement or malignancy. The antibodies can target both the alpha- and beta-chains of Mi-2. Isolated occurrence of antibodies against Mi-2 beta has low diagnostic value and can also be seen in healthy individuals.

TIF1γ (p155/140)

Antibodies against TIF1γ are associated with dermatomyositis and in adults (but rarely in children) strongly associated with malignancy, but not with interstitial lung disease. In children, anti-TIF1γ is linked to dermatomyositis without association with malignancy.

NXP2 (MJ)

Antibodies against NXP2 can be detected in patients with juvenile dermatomyositis and are associated with a severe course of pronounced muscle involvement (atrophy, contractures). Calcinosis, ulcerations and intestinal vasculitis also occur. Antibodies against NXP2 are associated with an increased risk of underlying malignancy in adults.

SAE1 (SUMO-1)

Antibodies against "small ubiquitin-like modifier activating enzyme" is a rare antibody in adults with dermatomyositis where the skin symptoms often precede the development of myositis. Interstitial lung disease can also occur. Anti-SAE is associated with malignancy.

MDA5

Antibodies against melanoma-differentiation-associated gene 5 (anti-MDA5) are strongly associated with severe and rapidly progressing interstitial lung disease in dermatomyositis where muscle weakness may be mild and CK (creatine kinase) normal (amyopathic dermatomyositis). Borderline values may also be of clinical significance. Anti-MDA5 is not associated with malignancy.

References

Satoh M. et al. Clinic Rev Allerg Immunol. 2017. A Comprehensive Overview on Myositis-Specific Antibodies: New and Old Biomarkers in Idiopathic Inflammatory Myopathy. PMID: 26424665
Fujimoto M et al. Curr Opin Rheumatol. 2016. Recent advances in dermatomyositis-specific autoantibodies. PMID: 27533321
Nakashima R et al. Lupus. 2016. Clinical significance and new detection system of autoantibodies in myositis with interstitial lung disease. PMID: 27252271
Trallero Arguas E et al. Semin Arthritis Rheum. 2016. Clinical manifestations and long-term outcome of anti-Jo1 antisynthetase patients in a large cohort of Spanish patients from the GEAS-IIM group. PMID: 27139168
Allenbach Y, Benveniste O. Journal of Neuromuscular Diseases 2. 2015. Diagnostic Utility of Auto-Antibodies in Inflammatory Muscle Diseases. PMID: 28198709
Ghirardello A et al. Autoimmun Highlights. 2014. Myositis autoantibodies and clinical phenotypes. PMID: 26000158
Beneviste et al. Arthritis Rheum. 2011. Correlation of anti-signal recognition particle autoantibody levels with creatine kinase activity in patients with necrotizing myopathy. PMID: 21400483
Belizna C et al. Autoimmunity Reviews. 2010. Anti-Ku antibodies: Clinical, genetic and diagnostic insights. PMID: 20621654
Gunawardena H, Betteridge ZE, McHugh NJ. Rheumatology. 2009. Myositis-specific autoantibodies: their clinical and pathogenic significance in disease expression. PMID: 19439503
Mahler M et al. Autoimmunity Reviews. 2007. Novel aspects of autoantibodies to the PM/Scl complex: clinical, genetic and diagnostic insights. PMID: 17643929
Lundberg IE et al. Ann Rheum Dis. 2017. European League Against Rheumatism/American College of Rheumatology classification criteria for adult and juvenile idiopathic inflammatory myopathies and their major subgroups. PMID: 29079590
Allenbach Y et al. Neuromuscul Disord. 2018. 224th ENMC International Workshop: Clinico-sero-pathological classification of immune-mediated necrotizing myopathies Zandvoort, The Netherlands, 14–16 October 2016. PMID: 29221629
Lundberg IE et al. Nat Rev Dis Primers. 2021. Idiopathic inflammatory myopathies. PMID: 34857780

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