[Two cases of statin-induced immune-mediated necrotizing myopathy]

Statin-induced immune-mediated necrotizing myopathy (IMNM) is a rare subtype of idiopathic inflammatory myopathy (IIM) that distinct from other types of IIM and statin-induced muscle symptoms, regarding clinic, diagnosis and treatment. The condition, characterized by symmetrical proximal muscle weakness and significantly increased creatine kinase (CK) levels, is persistent after statin discontinuation. Muscle biopsy shows necrotic muscle fibers and regeneration fibers with minimal inflammatory infiltrates. Over the past decade, an autoantibody to hydroxymethylglutaryl coenzyme A reductase (HMGCR) has been identified for the diagnosis of statin-associated IMNM. Optimal treatment strategy is unclear, but aggressive immunosuppression has shown to be effective. This case report describes two patients with statin-induced IMNM. The patients present with proximal muscle weakness, elevated CK levels, and are subsequently positive for anti-HMGCR autoantibodies with necrosis in muscle biopsy.