Statin-induced necrotizing autoimmune myopathy: An uncommon complication of a commonly used medication

A well-known side effect of statin therapy is myopathy. We report a case of statin induced necrotizing autoimmune myopathy, a rare variant of statin-induced myopathy. A 64-year-old gentleman on atorvastatin presented with muscle weakness. Initial laboratory results showed elevated liver function tests, a creatine phosphokinase (CPK) of 8200 IU/L, and positive urine myoglobin. Despite discontinuing atorvastatin, his CPK remained persistently elevated. Muscle biopsy was consistent with necrotizing myopathy. Anti-HMG CoA reductase antibody was strongly positive. Steroids followed by intravenous immunoglobulin were given. The patient’s muscle weakness, CPK, and liver functions gradually improved, and he was eventually discharged on oral steroids. Statin induced necrotizing autoimmune myopathy should be considered when discontinuing statin does not lead to muscle recovery and improvement in CPK. Diagnosis is confirmed by positive anti-HMG-CoA reductase autoantibody.