Amyopathic Dermatomyositis — SCE Dermatology MCQ

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HardConnective Tissue & VasculitisAmyopathic DermatomyositisSCE Dermatology

A 55-year-old woman is diagnosed with dermatomyositis and has extensive skin disease with minimal muscle involvement. Her CK is normal. Anti-MDA5 is positive. What is this clinical phenotype called?

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Correct answer: C — Clinically amyopathic dermatomyositis (CADM)

Clinically amyopathic dermatomyositis (CADM) presents with characteristic DM skin findings (heliotrope rash, Gottron papules, V-sign, shawl sign) but with minimal or absent clinical muscle involvement and normal or near-normal CK. Anti-MDA5 is the hallmark antibody associated with CADM. Crucially, anti-MDA5-positive CADM carries a high risk of rapidly progressive interstitial lung disease (RP-ILD), which can be fatal within months if not treated aggressively. Despite the absence of clinically significant myositis, these patients require urgent pulmonary assessment (HRCT, PFTs) and aggressive immunosuppression (triple therapy: corticosteroids + calcineurin inhibitor + cyclophosphamide) if ILD is detected.

Reference: BAD 2016 DM Guidelines; Rheumatology 2019