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Anti-MDA5 RP-ILD Risk — SCE Rheumatology MCQ

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HardMyositisAnti-MDA5 RP-ILD RiskSCE Rheumatology

A 60-year-old woman has ulcerated Gottron papules and painful palmar papules but no objective muscle weakness. Her creatine kinase is 300 U/L and anti-MDA5 antibodies are positive. She currently has no dyspnoea and her resting oxygen saturation is 97% on air. Which statement best explains why the limited muscle involvement should not be considered reassuring?

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Reveal the answer and explanation

Correct answer: D — Rapidly progressive interstitial lung disease may develop and drive early mortality independently of muscle disease severity

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

B is correct. Anti-MDA5 dermatomyositis commonly has an amyopathic or hypomyopathic phenotype, so creatine kinase and muscle strength may substantially underestimate overall disease severity. Its major prognostic complication is rapidly progressive interstitial lung disease, which can evolve over weeks to months and carries high early mortality. Normal resting oxygen saturation at presentation does not exclude evolving lung disease. Markedly raised CK and necrotising myopathy are more characteristic of anti-SRP or anti-HMGCR disease. Malignancy risk is more strongly associated with antibodies such as anti-TIF1γ, while antisynthetase antibodies define a different myositis-ILD phenotype and are not required for anti-MDA5 lung disease. Calcinosis and contractures are more characteristic of juvenile dermatomyositis than the principal early threat here.

Reference: Sehgal S et al. Idiopathic inflammatory myopathies related lung disease in adults. Lancet Respiratory Medicine. 2025; pulmonary manifestations and anti-MDA5-associated ILD sections. https://pubmed.ncbi.nlm.nih.gov/39622261/