A 70-year-old male with a two-year history of weakness and dysphagia was diagnosed with immune-mediated necrotizing myopathy (IMNM) (Figure 1) confirmed by biopsy and SRP autoantibody positivity. He failed treatment with steroids, azathioprine, and IVIG, leading to wheelchair dependence, profound proximal weakness, dysphonia, and dysphagia. Labs showed Creatinine Phosphokinase (CPK) of two thousand four hundred and sixty-nine U/L (2469 U/L) and SRP antibody was hundred and thirteen SI (113 SI units) (10x upper limit). Diagnosed with severe acute necrotizing myopathy 10 months ago (2/26/2024 (Figure 2 & 3) Rituximab was initiated. Remarkably, he regained independent gait, arm strength, speech, and swallowing.

SRP-positive autoimmune-mediated necrotizing myopathy (IMNM) is a severe subtype of immune-mediated necrotizing myopathy, distinct from anti-Hydroxy-3-Methylglutaryl-CoA Reductase (HMGCR) (better prognosis) autoantibody-associated IMNM and autoantibody-negative IMNM. IMNM falls under the broader category of inflammatory myositis. The four differentials include polymyositis, dermatomyositis, and inclusion body myositis]. Other causes of proximal myopathies include McArdle’s disease, thyroid disorders, and statin induced myopathy.

Ethics approval

Inspira Health IRB, Inspira Medical Center IRB.

Author contributions

Conceptualization and writing, Formal analysis, Investigation, S Soloway. Date collection, V Goonssinghe.

The author has read and agreed to the published version of manuscript.

Data availability statement

All data are HIPPA protected and available upon request.