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Anti-SRP Myopathy — RACP Adult Medicine MCQ

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HardRheumatologyAnti-SRP MyopathyRACP Adult Medicine

A 48-year-old woman presents with bilateral symmetrical proximal muscle weakness. CK is 8,500 U/L. She has no skin rash. Anti-SRP antibodies are positive. EMG shows myopathic changes. What is the expected treatment response?

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Correct answer: C — Poor response to corticosteroids – aggressive immunosuppression with rituximab or IVIg required

Anti-SRP (signal recognition particle) myopathy is a necrotising autoimmune myopathy characterised by severe proximal weakness, very high CK, and poor response to corticosteroids alone. It requires aggressive combination immunosuppression – typically IVIg and/or rituximab. Anti-SRP myopathy has a worse prognosis than classic polymyositis or dermatomyositis and often requires long-term immunosuppression. Muscle biopsy shows myofibre necrosis with minimal inflammation.

Reference: eTG – 2025 – Rheumatology; ENMC – 2017 – Necrotising Autoimmune Myopathy Criteria