Immune-mediated necrotising myopathy in asymptomatic patients with high creatine kinase.

Subacute symmetrical proximal muscle weakness and persistent elevated creatine kinase levels are typical of immune-mediated necrotising myopathy (IMNM). These conditions are accompanied by copious myofibre necrosis, degeneration and regeneration with minimal to no inflammation on muscle biopsy. We report two cases (case 1 and case 2) of asymptomatic IMNM from different families with hyperCKaemia associated with positive anti-signal recognition particle (SRP) and anti-3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR) antibodies, respectively, and we also reviewed the literature. There are only a few previous descriptions of patients with asymptomatic IMNM.The disease onset could be insidious and lead to delayed diagnosis and treatment. We recommend testing for the anti-HMGCR and anti-SRP antibodies in patients with idiopathic hyperCKaemia because they could show no symptoms of this disorder. © BMJ Publishing Group Limited 2020. No commercial re-use. See rights and permissions. Published by BMJ.