Anti-HMGCR Myopathy: A Rare and Serious Side Effect of Statins

Cardiovascular disease is a leading cause of morbidity and mortality in the United States. Since their initial discovery, statins have become the first-line treatment for decreasing the risk of cardiovascular disease. Although they are typically well tolerated, side effects do occur and tend to affect the musculature. Most side effects are benign and resolve after discontinuing the statin. A subset of immune-mediated necrotizing myositis, anti-3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR) myopathy is a rare disease that occurs in 0.9 to 1.4 cases per 100,000 people. It causes significant muscle weakness that does not resolve with discontinuation of the statin. Unlike other known complications, it has a late onset, occurring years after the statin was initially prescribed. It can also present in patients previously treated with statins who have not taken them for several years. This case report details the case of a 54-year-old woman who developed anti-HMGCR myopathy after several years of uncomplicated statin use. Differences between other reported cases and this 1 are discussed, including the patient's strong response to steroid therapy which resulted in the normalization of her serum creatinine kinase and alleviation of her muscle weakness. This case highlights the need for clinicians to be aware of anti-HMGCR myopathy and to consider it as a potential cause of proximal muscle weakness and persistent serum creatinine kinase elevations in patients exposed to statins even if they were previously well tolerated by the patient.