Statin-Induced Immune-Mediated Necrotizing Myopathy: A Case Report of a Rare and Underrecognized Cause of Progressive Weakness

Statin-induced necrotizing autoimmune myopathy is a rare immune-mediated process that leads to muscle necrosis and occurs following exposure to statin therapy. The diagnostic clue for this disorder stems from the development of a proximal muscle weakness associated with the elevation of creatine kinase levels in association with the use of statin medication. Management mainly includes discontinuation of the statin medication, pursuing a tissue diagnosis, and early initiation of immunosuppressive therapy to preserve and regain muscle strength. We present the case of a 54-year-old patient with statin-induced necrotizing autoimmune myopathy who developed proximal muscle weakness a few months after initiation of statin therapy, was positive for anti-HMGCR (anti-hydroxy-methyl-glutaryl coA reductase) autoantibodies, and had evidence of muscle necrosis with minimal cellular infiltration on muscle biopsy. A definitive diagnosis can often be made without biopsy in the presence of positive anti-HMGCR antibodies and a compatible clinical presentation, though biopsy remains valuable for seronegative or atypical cases. He was treated with immunosuppressive therapy using intravenous immunoglobulins and was noted to have a good response. This case report highlights the importance of early recognition of statin-related adverse effects that require urgent evaluation and timely therapy to preserve and improve the functional status of a patient.