Statin-Associated Immune-Mediated Necrotizing Myopathy With Dual Anti-3-Hydroxy-3-Methylglutaryl-Coenzyme A Reductase (Anti-HMGCR) and Anti-OJ Positivity: A Case Report of Fulminant Weakness and Respiratory Failure

Immune-mediated necrotizing myopathy (IMNM) is a rare and aggressive form of idiopathic inflammatory myopathy, which is often associated with statin exposure and myositis-specific antibodies such as anti-HMGCR or anti-synthetase antibodies. It is characterized by rapidly progressive muscle weakness, markedly elevated creatine kinase (CK), and often significant morbidity due to respiratory or bulbar involvement. We share the story of a 71-year-old man with type 2 diabetes mellitus, asthma, chronic kidney disease, and hypercholesterolemia who presented with progressive weight loss and difficulty in walking. He was on Atorvastatin for elevated cholesterol levels. His condition rapidly worsened, leading to lower limb weakness, dysphagia, and recurrent type 2 respiratory failure, requiring prolonged non-invasive ventilation. Electromyography, lower limb MRI, showed features of polymyositis, and biopsy confirmed IMNM. Serology was positive for anti-HMG-CoA (3-hydroxy-3-methylglutaryl-coenzyme A) reductase and anti-OJ antibodies. He was treated with high-dose corticosteroids, mycophenolate, and intravenous immunoglobulin. His hospital course was complicated by aspiration pneumonia, paroxysmal atrial fibrillation, and severe dysphagia requiring gastrostomy feeding. With intensive multidisciplinary care, including respiratory, rheumatology, physiotherapy, and speech therapy, he gradually improved in respiratory function and mobility, regaining upper limb strength and partial independence at discharge. This case demonstrates the diagnostic complexity of IMNM, the need for early recognition in patients with statin exposure and rapidly progressive weakness, and the importance of aggressive immunosuppression alongside comprehensive multidisciplinary care. Despite multiple complications, meaningful functional recovery is possible with timely and coordinated management.