Disclosures: Kelsey R. Whitus: No financial relationships or conflicts of interest

Case Diagnosis: Statin-Associated Immune-Mediated Necrotizing Myopathy (IMNM)

Case Description or Program Description: A 73-year-old female with a history of hyperlipidemia and osteoporosis, presented to her primary care physician complaining of muscle pain and fatigue for four weeks. Patient reports taking atorvastatin for one-year. She discontinued atorvastatin two weeks prior to the office visit, leading to slight improvement of symptoms. Laboratory work up revealed an elevated creatinine kinase (CK). She was referred to the emergency room and was admitted for rhabdomyolysis. Hospital course comprised of multidisciplinary interventions. Physiatry performed an electrodiagnostic study in which the findings were consistent with an underlying myopathic process. Rheumatology ordered an extended myositis panel, and she was found to be positive for 3-hydroxy-3-methylglutaryl-coenzyme A reductase antibody (anti-HMGCR). She was treated with intravenous fluids, corticosteroids, and immunosuppressants.

Setting: Acute care Hospital

Assessment/Results: One month following discharge she reports feeling fifty percent better and is working with physical therapy twice a week. She is currently ambulating without assistance. CK has normalized since hospitalization. Patient continues to make gradual improvement.

Discussion (relevance): The diagnosis of Statin-Associated Immune-Mediated Necrotizing Myopathy (IMNM) is based on the detection of antibodies against HMGCR. Positive anti-HMGCR findings allows for the ability to differentiate IMNM from Self-Limited Statin Myopathy. Anti-HMGCR IMNM has an association with an environmental trigger (statin-mediated), and a genetic background (HLA-DRB1*11:01). The predominant feature on muscle biopsy is necrotic muscle fibers with limited inflammatory infiltrate.

Conclusions: Physicians should be aware of this rare, however serious, side effect of statin therapy. Patients typically present with subacute onset, progressive, symmetric proximal muscle weakness with significantly elevated CK levels that persists for months after discontinuation of statins. Definitive diagnosis can be made with muscle biopsy. Early recognition and prompt intervention is of the utmost importance for better outcomes in return of function.

Level of Evidence: Level V

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PM&R Meeting Abstracts - https://pmrjabstracts.org/abstract/statin-associated-immune-mediated-necrotizing-myopathy-in-a-patient-on-atorvastatin-a-case-report/