(Kiosk 2) Statin-induced Immune-mediated Necrotizing Myopathy: A Case Report

Case Diagnosis: Statin-Induced Autoimmune Necrotizing Myopathy

Case Description or Program Description: This patient had been receiving atorvastatin 80mg for many years. He presented with rapidly progressive, symmetric proximal greater than distal weakness in all extremities over the course of a month, resulting in inability to walk. He also developed difficulty swallowing and a hoarse voice. Examination showed hypophonia, atrophic tongue, proximal limb weakness in all extremities and diminished tendon reflexes. He was found to have elevated creatine phosphokinase (>10,000) and muscle inflammation on leg MRI. High-dose parenteral steroids were initiated, followed by intravenous immunoglobulin, methotrexate, and prednisone. Subsequent results were positive for anti-HMGCR antibodies on serology as well as myositis on muscle biopsy, all consistent with immune-mediated necrotizing myopathy.

Setting: Secondary Care Hospital

Assessment/Results: Treatment rapidly normalized his CPK. Despite ongoing medication and physical therapy, weakness, dysphagia, and ambulatory dysfunction have persisted, complicated by falls and aspiration pneumonia. He has also developed rapid atrial fibrillation, and remains in the acute care hospital over the past 6 weeks.

Discussion (relevance): This case demonstrates an atypical and rare form of statin myopathy. Typical statin-associated myopathy causes muscle pain that resolves with discontinuation of medication. This case involves an immune-mediated process that led to weakness, without significant pain, and other symptoms including dysphagia. Rapidly progressive weakness may lead to suspicion of other neuromuscular conditions. The current diagnosis should be on the differential for patients using statins presenting with these symptoms.

Conclusions: Statin use may lead to autoimmune-mediated necrotizing myopathy that can persist after discontinuation of offending medication. Ideal management is not currently clear, although steroids, IVIG and methotrexate are indicated.