Thigh muscle MRI in immune-mediated necrotising myopathy: extensive oedema, early muscle damage and role of anti-SRP autoantibodies as a marker of severity

• Published in: Annals of the rheumatic diseases Vol. 76; no. 4; pp. 681 - 687
• Main Authors: Pinal-Fernandez, Iago, Casal-Dominguez, Maria, Carrino, John A, Lahouti, Arash H, Basharat, Pari, Albayda, Jemima, Paik, Julie J, Ahlawat, Shivani, Danoff, Sonye K, Lloyd, Thomas E, Mammen, Andrew L, Christopher-Stine, Lisa
• Format: Journal Article
• Language: English
• Published: United States Elsevier Limited 01.04.2017
• Subjects: Adiposity; Adult; Aged; Antibodies - blood; Atrophy - diagnostic imaging; Biomarkers - blood; Dermatomyositis - diagnostic imaging; Edema; Edema - diagnostic imaging; Female; Humans; Hydroxymethylglutaryl CoA Reductases - immunology; Kinases; Magnetic Resonance Imaging; Male; Middle Aged; Muscle, Skeletal - diagnostic imaging; Muscle, Skeletal - pathology; Muscular Diseases - blood; Muscular Diseases - diagnostic imaging; Muscular Diseases - immunology; Myositis, Inclusion Body - diagnostic imaging; Necrosis - blood; Necrosis - diagnostic imaging; Necrosis - immunology; Patients; Polymyositis - diagnostic imaging; Predictive Value of Tests; Severity of Illness Index; Signal Recognition Particle - immunology; Studies; Thigh; Magnetic Resonance Imaging; Polymyositis; Autoantibodies; Dermatomyositis
• ISSN: 0003-4967; 1468-2060; 1468-2060
• DOI: 10.1136/annrheumdis-2016-210198

ObjectivesThe aims of this study were to define the pattern of muscle involvement in patients with immune-mediated necrotising myopathy (IMNM) relative to those with other inflammatory myopathies and to compare patients with IMNM with different autoantibodies.MethodsAll Johns Hopkins Myositis Longitudinal Cohort subjects with a thigh MRI (tMRI) who fulfilled criteria for IMNM, dermatomyositis (DM), polymyositis (PM), inclusion body myositis (IBM) or clinically amyopathic DM (CADM) were included in the study. Muscles were assessed for intramuscular and fascial oedema, atrophy and fatty replacement. Disease subgroups were compared using univariate and multivariate analyses. Patients with IMNM with anti-signal recognition particle (SRP) autoantibodies were compared with those with IMNM with anti-HMG-CoA reductase (HMGCR) autoantibodies.ResultsThe study included 666 subjects (101 IMNM, 176 PM, 219 DM, 17 CADM and 153 IBM). Compared with DM or PM, IMNM was characterised by a higher proportion of thigh muscles with oedema, atrophy and fatty replacement (p<0.01). Patients with IMNM with anti-SRP had more atrophy (19%, p=0.003) and fatty replacement (18%, p=0.04) than those with anti-HMGCR. In IMNM, muscle abnormalities were especially common in the lateral rotator and gluteal groups. Fascial involvement was most widespread in DM. Fatty replacement of muscle tissue began early during the course of disease in IMNM and the other groups. An optimal combination of tMRI features had only a 55% positive predictive value for diagnosing IMNM.ConclusionsCompared with patients with DM or PM, IMNM is characterised by more widespread muscle involvement. Anti-SRP-positive patients have more severe muscle involvement than anti-HMGCR-positive patients.