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Dermatomyositis – Anti-Mi-2 Subtype — SCE Neurology MCQ

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ModeratePeripheral Neuropathy & NeuromuscularDermatomyositis – Anti-Mi-2 SubtypeSCE Neurology

A 55-year-old man presents with 3 months of progressive bilateral proximal arm weakness, neck flexor weakness, and dysphagia. CK is 8,500 IU/L. He has a heliotrope rash around his eyelids and a V-sign erythema on his anterior chest. Anti-Mi-2 antibodies are positive. CT chest/abdomen/pelvis shows no malignancy. What is the diagnosis and what is the expected treatment response?

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Correct answer: D — Dermatomyositis (anti-Mi-2 subtype) — this subtype has a particularly good response to immunosuppressive therapy

Anti-Mi-2 antibodies define a subtype of dermatomyositis characterised by classic DM skin features (heliotrope rash, Gottron papules, V-sign, shawl sign), proximal weakness, elevated CK, and importantly, a particularly good response to immunosuppressive therapy (better than other DM subtypes like anti-MDA5 or anti-NXP2). This antibody positivity is associated with a lower malignancy risk compared with other DM subtypes. Treatment is prednisolone + steroid-sparing agent (azathioprine, methotrexate, mycophenolate). A: IBM does not respond to steroids and lacks DM skin features. C: Statin myopathy resolves on cessation. D: PMR has normal CK. E: Dystrophies are genetic.

Reference: ABN Inflammatory Myopathy Guidelines; ENMC DM Classification