Abstract 16715: Rare or Disregarded; A Case of Autoimmune Myopathy

Abstract

Introduction: Statin-induced myopathy can present with symptoms ranging from mild myalgia to significant muscle weakness. This case report highlights how statin-induced autoimmune myopathy often goes undiagnosed. Case Presentation: We present a 69 year old male with a past medical history of coronary artery disease who presented with myalgia and progressive proximal muscle weakness for 2 months. On admission, creatinine kinase (CK) level was noted to be elevated at 8323 u/L. Atorvastatin was held on admission and the patient received intravenous (IV) fluid as treatment for presumed rhabdomyolysis. Although CK was trending down, the patient did not show any significant improvement in muscle weakness or myalgia. At this point, myositis was suspected, so a myositis panel including anti-HMG Co-A Reductase antibody was ordered and the patient was started on IV steroids. Anti-HMG Co-A Reductase antibody was positive and the rest of myopathy workup was negative; meanwhile, the patient's muscle weakness significantly improved. The patient was discharged on a methylprednisolone with close outpatient rheumatology follow-up. Discussion: Drug-induced rhabdomyolysis is one of many causes of myalgia. It is crucial to review a patient’s medication list and discontinue any possible medications that are possible offenders. Statin-induced myopathy should also be suspected when typical treatment for rhabdomyolysis is failing. Statin induced autoimmune myopathy is associated with muscle weakness, elevated CK and a positive anti-HMG Co-A Reductase antibody, which requires discontinuation of Statin and initiation of immunosuppressive therapy. Conclusions: This case report highlights the importance of early identification and management of statin-induced autoimmune myopathy as a possible differential diagnosis in patients with muscle weakness, elevated CK levels while on statin therapy who do not respond to IV fluid alone.