Discussion: IMNM is a rare and serious condition that is distinct from other myopathies, such as polymyositis or inclusion-body myositis. Patients typically present with proximal muscle weakness and myalgia, which persists even after statin therapy is discontinued. Severe cases can lead to dysphagia or diaphragmatic weakness causing respiratory distress. Laboratory data is significant for an elevated CK level, and mild transaminase elevation. EMG findings are consistent with a myopathic process and MRI will show evidence of muscle edema. On histology, IMNM classically displays myofiber necrosis and regeneration, with minimal lymphocyte infiltration. This constellation of findings supports a diagnosis of IMNM. Autoantibodies against 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase are present in the biopsy specimens of the majority of patients exposed to statins, confirming the diagnosis of statin-induced IMNM. Patients are initially treated with corticosteroids and may require additional immunosuppressive agents, depending on the severity of the weakness and the initial response to steroid treatment.
Conclusions: IMNM is a rare but clinically important diagnosis. The majority of prescribers of statin therapy are internists and cardiologists, most of whom are unaware of this condition. It is essential for clinicians to consider IMNM in the differential when symmetrical proximal weakness persists after statin cessation.
To cite this abstract:Ward, RC; Ning, WV; Dowlatshahi, S . WHY DO MY MUSCLES STILL ACHE? A RARE COMPLICATION OF STATIN THERAPY. Abstract published at Hospital Medicine 2017, May 1-4, 2017; Las Vegas, Nev. Abstract 784. Journal of Hospital Medicine. 2017; 12 (suppl 2). https://www.shmabstracts.com/abstract/why-do-my-muscles-still-ache-a-rare-complication-of-statin-therapy/. Accessed September 23, 2019.