Myositis antibody profile — SCE Rheumatology MCQ

Instant feedback + full explanation. One question, done properly.

HardMusculoskeletal InvestigationsMyositis antibody profileSCE Rheumatology

A 53-year-old woman has dermatomyositis with severe cutaneous disease and rapidly progressive interstitial lung disease. CK is only mildly elevated. Myositis panel shows anti-MDA5 antibody. Infection has been excluded. What is the most likely diagnosis?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: C — Anti-MDA5 dermatomyositis

Explanation lettering: C = shown as A · A = shown as B · D = shown as C · E = shown as D · B = shown as E

Anti-MDA5 dermatomyositis is best because anti-MDA5 is linked to dermatomyositis with severe skin disease and rapidly progressive ILD, sometimes with modest CK. A is less suitable because anticentromere relates to limited systemic sclerosis and PAH risk; B is less suitable because anti-SRP causes severe necrotising myopathy with high CK; C is less suitable because anti-HMGCR causes necrotising myopathy often with marked CK; E is less suitable because anti-Mi-2 is associated with classic rash and good treatment response but less RP-ILD phenotype. Clinical pearl: myositis antibodies should be interpreted by phenotype, not as isolated laboratory labels.

Reference: BSR idiopathic inflammatory myopathy guideline 2022; ERS/EULAR CTD-ILD guidance