SHM Converge Scientific Abstract ePoster Gallery-A Rare Case of Anti-Signal Recognition Particle Positive Immune-Mediated Necrotizing Myopathy

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This case report describes a 61-year-old man with hypertension who developed subacute, progressively worsening proximal muscle weakness over three months. His symptoms included difficulty walking, wheelchair dependence, trouble holding up his head, and dysphagia. Examination showed marked weakness in shoulder abduction and hip flexion without rash or arthritis. Initial labs revealed elevated creatine kinase and transaminitis.<br /><br />MRI demonstrated symmetric diffuse edema and moderate atrophy of the pelvic girdle and thigh muscles, especially the adductor compartments. CT chest/abdomen/pelvis was negative for malignancy, though fluid was seen in the intramuscular planes of the thighs. Autoimmune testing showed ANA 1:1280 and a positive anti-SRP antibody. Muscle biopsy from the quadriceps and deltoid showed scattered necrotic and regenerative fibers with minimal inflammation, and MHC class I staining showed patchy upregulation. Pathology confirmed necrotizing autoimmune myopathy, specifically the anti-SRP subtype of immune-mediated necrotizing myopathy (IMNM).<br /><br />The patient was treated with five days of IVIG and a steroid taper. He improved slightly, was evaluated by therapy, and was discharged to rehabilitation. The report emphasizes that anti-SRP IMNM is a rare inflammatory myopathy, accounting for less than one-fifth of IMNM cases, and is associated with more severe weakness, higher CK levels, poorer response to steroids, and worse long-term muscle recovery due to early fatty replacement.<br /><br />The objective of the report is to expand the differential diagnosis of myopathy, review this uncommon inflammatory myopathy, and promote early recognition and treatment to prevent irreversible muscle damage.

Asset Subtitle

Nikhil Seth

Meta Tag

Author List Angela Liu, Nikhil Seth

Category Clinical Vignettes

Concept Immune-Mediated Necrotizing Myopathy

Concept Proximal Weakness

Concept Anti-SRP Antibody

Concept Creatine Kinase

Concept Muscle Biopsy

Distinguished Non-Finalist

Presenter Organization Baylor College of Medicine

Presenting Author Nikhil Seth

Track Adult

Keywords

anti-SRP

immune-mediated necrotizing myopathy

necrotizing autoimmune myopathy

proximal muscle weakness

elevated creatine kinase

muscle biopsy

IVIG treatment

dysphagia

MRI muscle edema

inflammatory myopathy

Immune-Mediated Necrotizing Myopathy

Proximal Weakness

Anti-SRP Antibody

Creatine Kinase

Muscle Biopsy