Statin-Associated Immune-Mediated Necrotizing Myopathy: An Underrecognised Cause of Progressive Muscle Weakness in Primary Care

Statins are among the most frequently prescribed agents in primary care for lipid control and cardiovascular risk reduction. Although generally safe, they are associated with muscle-related adverse effects, ranging from myalgia and self-limiting myopathy to the rare but clinically significant immune-mediated necrotizing myopathy (IMNM). We report a 52-year-old congenitally deaf and mute Chinese man with diabetes, hypertension, and dyslipidaemia who had been on atorvastatin since 2020 and presented with progressive proximal muscle weakness over one year, more prominent in the lower limbs, accompanied by unintentional weight loss. Communication barriers and the absence of classical features of rhabdomyolysis contributed to delayed recognition of an underlying inflammatory myopathy. Laboratory investigations revealed markedly elevated creatine kinase levels, and muscle biopsy confirmed IMNM with strong anti-HMG-CoA (anti-3-hydroxy-3-methylglutaryl-coenzyme A) reductase antibody positivity. The patient responded well to high-dose corticosteroids, with recovery of muscle strength and normalisation of enzyme levels. This case highlights a diagnostic challenge in primary care, where statin-induced myopathy is a common consideration, while statin-associated IMNM remains underrecognised in clinical practice.