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Inclusion Body Myositis — SCE Neurology MCQ

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ModeratePeripheral Neuropathy & NeuromuscularInclusion Body MyositisSCE Neurology

A 70-year-old man presents with 18 months of progressive weakness affecting finger flexors bilaterally and left quadriceps. CK is mildly elevated (500 IU/L). Muscle biopsy shows rimmed vacuoles and inflammatory infiltrates with invasion of non-necrotic fibres. He has not responded to a trial of prednisolone. What is the most likely diagnosis?

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Correct answer: E — Inclusion body myositis

Inclusion body myositis (IBM) is the most common acquired myopathy in patients over 50 years. Characteristic features include asymmetric weakness of finger flexors (particularly flexor digitorum profundus) and quadriceps, mildly elevated CK, rimmed vacuoles on biopsy, and poor response to immunosuppression. A: Polymyositis causes symmetric proximal weakness and responds to steroids. B: Dermatomyositis has characteristic skin features. D: MG causes fatigable weakness, not progressive wasting. E: LGMD presents with proximal weakness in younger patients.

Reference: ABN Inflammatory Myopathy Guidelines; EAN/EFNS IBM Guidelines