Necrotising Myopathy — SCE Rheumatology MCQ

Correct answer: B — Rapidly progressive severe proximal weakness, markedly elevated CK and myofibre necrosis with sparse inflammation

Anti-SRP antibodies define a major serological subtype of immune-mediated necrotising myopathy. The characteristic phenotype is acute or subacute, often severe symmetrical proximal weakness with markedly elevated CK; biopsy typically shows prominent myofibre necrosis and regeneration with relatively sparse inflammatory infiltrates. Dysphagia may occur, and the disease can be refractory. Option D describes an antisynthetase-antibody phenotype, while option E suggests scleromyositis, often associated with antibodies such as anti-PM/Scl. Option A describes inclusion body myositis. Option C is characteristic of anti-MDA5 dermatomyositis. Interstitial lung disease can occasionally occur with anti-SRP disease, so its presence is not absolutely exclusionary, but it is not the defining phenotype.

Reference: Ma X, Bu BT. Anti-SRP immune-mediated necrotizing myopathy: A critical review of current concepts. Front Immunol. 2022;13:1019972. https://pubmed.ncbi.nlm.nih.gov/36311711/