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Classic Dermatomyositis — RACP Adult Medicine MCQ

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ModerateRheumatologyClassic DermatomyositisRACP Adult Medicine

A 45-year-old woman presents with symmetric proximal weakness, heliotrope rash, Gottron papules, and elevated CK (6000 U/L). Anti-Mi-2 antibody is positive. CT chest/abdomen/pelvis shows no malignancy. Muscle biopsy shows perifascicular atrophy with perimysial inflammatory infiltrate. What is the most likely inflammatory myopathy subtype?

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Correct answer: C — Dermatomyositis (classic)

Proximal weakness with heliotrope rash, Gottron papules, elevated CK, anti-Mi-2 (DM-specific antibody with good prognosis), and perifascicular atrophy on biopsy is classic dermatomyositis. Anti-Mi-2 DM has the best prognosis among DM subtypes and lowest malignancy association. Treatment: prednisolone + azathioprine or methotrexate. Age-appropriate malignancy screening is still required but may be less intensive than anti-TIF1γ or anti-NXP2 DM.

Reference: ACR/EULAR – 2017 – IIM Classification; eTG Rheumatology 2024