A Case of Anti-SRP Immune-mediated Necrotizing Myopathy Following Suspected Coxsackie B4 Infection: Exploring a Viral Trigger Hypothesis.

Immune-mediated necrotizing myopathy (IMNM) is a rare subtype of idiopathic inflammatory myopathies that can present with rhabdomyolysis. We report a 43-year-old woman with rapidly progressive proximal muscle weakness following a flu-like illness. Laboratory evaluation revealed markedly elevated creatine kinase (22,207 U/L) and transaminases, with positive anti-signal recognition particle (SRP) and Coxsackie B4 antibodies. Muscle biopsy demonstrated extensive necrosis, regeneration, and endomysial lymphocytic infiltration, confirming IMNM. The patient was treated with intravenous methylprednisolone, IVIG, and rituximab, followed by oral steroid taper and mycophenolate. At six-month follow-up, she showed significant clinical and biochemical improvement. This case highlights a potential viral-triggered autoimmune mechanism, suggesting that Coxsackie B4 infection may initiate or amplify anti-SRP-mediated immune muscle injury. Greater awareness of viral associations may aid early diagnosis and targeted therapy of IMNM.