Immune-Mediated Necrotizing Myopathy With Anti-3-Hydroxy-3-Methylglutaryl-CoA Reductase (HMGCR) Antibodies Following Viral Infection and Without Association With Statin Use: A Case Report

Immune-mediated necrotizing myopathy (IMNM) is a rare form of inflammatory myopathy characterized by severe muscle weakness, elevated serum creatine kinase (CK) levels, and myofiber necrosis with minimal inflammatory infiltrates. IMNM is frequently associated with autoantibodies, particularly anti-3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR), and is often linked to statin use. However, it can also develop in statin-naïve patients, especially following viral infections. We present the case of a 47-year-old woman who developed anti-HMGCR-positive IMNM without prior statin exposure, following a viral respiratory infection and subsequent dengue fever. She initially presented with proximal muscle weakness and elevated CK levels, which worsened after contracting dengue. Diagnostic testing confirmed the presence of anti-HMGCR antibodies, and a muscle biopsy revealed necrotizing myopathy. Treatment with methylprednisolone, intravenous immunoglobulin, and rituximab resulted in significant clinical improvement. This case underscores the need to consider IMNM in patients with unexplained muscle weakness and elevated CK levels, even in the absence of statin use. Viral infections may trigger IMNM, highlighting the importance of early recognition and aggressive immunosuppressive therapy to prevent severe complications. Further research is required to better understand the pathophysiology of IMNM and optimize treatment approaches.