Immune-mediated necrotising myopathy: A critical review of current concepts

• Published in: Seminars in arthritis and rheumatism Vol. 49; no. 3; pp. 420 - 429
• Main Authors: Day, Jessica A., Limaye, Vidya
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.12.2019
• Subjects: Idiopathic inflammatory myopathy; Immune-mediated necrotising myopathy; Immune-mediated necrotizing myopathy; Myositis; Necrotising autoimmune myopathy; Idiopathic inflammatory myopathy; Myositis; Immune-mediated necrotizing myopathy; Necrotising autoimmune myopathy; Immune-mediated necrotising myopathy
• ISSN: 0049-0172; 1532-866X; 1532-866X
• DOI: 10.1016/j.semarthrit.2019.04.002

Immune-mediated necrotising myopathy (IMNM) is a relatively recently described form of idiopathic inflammatory myopathy (IIM) that is characterised by progressive proximal weakness and few extra-muscular manifestations. Prominent myonecrosis, muscle fibre regeneration and a relative paucity of intramuscular lymphocytes are seen histologically. Immunological mechanisms are believed to underpin the pathogenesis, and intense immunotherapy is frequently required. Disease is often severe and neuromuscular recovery may be poor. Recently there has been an impressive international research effort to understand and characterise this emerging condition, although much remains unknown. Significant advances in the field include the discovery of specific autoantibodies, increased understanding of the risk factors, clinical characteristics and treatment options owing to a wealth of observational studies, and the development of novel classification criteria. Herein we review the current evidence regarding the pathophysiology, clinical presentation, histological features and serological profiles associated with this condition. Diagnostic approaches are discussed, including the role of muscle MRI and antibodies targeting 3‑hydroxy-3-methylglutaryl-CoA reductase (HMGCR) and signal-recognition peptide (SRP), and a review of current treatment recommendations is provided.