SHM Converge Scientific Abstract ePoster Gallery-Statin-Induced Autoimmune Necrotizing Myopathy: An Uncommon Diagnosis for a Patient Presenting With Rhabdomyolysis

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This case describes a 54-year-old man with 6 weeks of progressive generalized weakness, especially proximal weakness in both upper and lower extremities, while taking atorvastatin started one year earlier. Initial labs showed severe rhabdomyolysis and muscle injury, including markedly elevated creatine kinase (30,802 U/L), AST/ALT over 1,000 U/L, elevated ESR, and myoglobinuria. Viral hepatitis and acetaminophen testing were negative. He was admitted for presumed rhabdomyolysis and treated with IV fluids, but symptoms did not improve.<br /><br />Further evaluation with EMG showed proximal myopathy with myonecrosis, inflammation, and vacuolization. His HMG-CoA reductase antibody was strongly positive, confirming statin-induced necrotizing autoimmune myopathy (SINAM), a rare but serious complication of statin therapy. Treatment required stopping the statin and escalating immunosuppression: IV methylprednisolone, IVIG, mycophenolate mofetil, and rituximab. He had only partial improvement and remained hospitalized for a prolonged period due to persistent weakness and inability to care for himself. He was eventually discharged to skilled nursing care and continued IVIG after discharge.<br /><br />The report emphasizes that SINAM is uncommon, potentially life-threatening, and can occur even long after statin initiation—up to 10 years after starting therapy. Unlike typical statin myalgias, symptoms do not resolve simply by stopping the drug. Diagnosis should be considered in patients with weakness and rhabdomyolysis who have current or prior statin exposure. Prognosis is often slow, with average remission taking around eight months and fewer than half of patients returning to baseline function.

Asset Subtitle

Michael Brandt

Meta Tag

Author List Chris Stephenson, Michael Brandt, Yvonne Bui

Category Clinical Vignettes

Concept Statin-induced necrotizing autoimmune myopathy

Concept Proximal Muscle Weakness

Concept Rhabdomyolysis

Concept Anti-HMGCR Antibody

Concept Statin

Distinguished Non-Finalist

Presenter Organization Mayo Clinic Rochester

Presenting Author Michael Brandt

Track Adult

Keywords

statin-induced necrotizing autoimmune myopathy

SINAM

atorvastatin

rhabdomyolysis

proximal muscle weakness

HMG-CoA reductase antibody

myositis

creatine kinase elevation

immunosuppression

IVIG

Statin-induced necrotizing autoimmune myopathy

Proximal Muscle Weakness

Rhabdomyolysis

Anti-HMGCR Antibody

Statin