Anti-3-Hydroxy-3-Methylglutaryl Coenzyme A Reductase (Anti-HMG CoA) Myopathy With Cardiac Involvement: Presentation, Diagnosis, and Management

Immune-mediated necrotizing myopathy (IMNM) is categorized into three groups: anti-3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR) IMNM, anti-signal recognition particle (SRP) IMNM, and seronegative IMNM. Cardiac involvement has been reported in a significant segment of patients with IMNM of the anti-SRP type. Emerging evidence now suggests that cardiac involvement is also implicated in the anti-HMGCR subgroup. In this report, we present a case of anti-HMGCR IMNM with cardiac involvement demonstrated by elevated troponin levels, a low ejection fraction of 40%, and regional wall motion abnormalities in the inferior, inferolateral, anteroseptal, inferoseptal, and anterolateral myocardial walls, as visualized on echocardiography. These findings markedly improved after treatment with intravenous immunoglobulin (IVIG) and prednisone. This case and other recent reports highlight the need for a cardiac workup in patients diagnosed with anti-HMGCR IMNM.