Diagnostic modelling and therapeutic monitoring of immune-mediated necrotizing myopathy: role of electrical myotonia

• Published in: Brain communications 2020-01, Vol.2 (2), p.fcaa191-fcaa191
• Main Authors: Triplett, James D, Shelly, Shahar, Livne, Guy, Milone, Margherita, Kassardjian, Charles D, Liewluck, Teerin, Kelly, Cecilia, Naddaf, Elie, Laughlin, Ruple S, Lamb, Christopher J, Rubin, Devon, Dimberg, Elliot L, Dubey, Divanshu, Mills, John R, Mandrekar, Jay, Klein, Christopher J
• Format: Article
• Language: English
• Subjects: Original
• ISSN: 2632-1297; 2632-1297
• DOI: 10.1093/braincomms/fcaa191

Abstract Delayed diagnosis of immune-mediated necrotizing myopathy leads to increased morbidity. Patients with the chronic course without 3-hydroxy-3-methylglutaryl-coenzyme-A reductase-IgG or signal recognition particle-IgG are often challenging to diagnose. Immunotherapy response can also be difficult to assess. We created a statistical model to assist immune-mediated necrotizing myopathy diagnosis. Electrical myotonia versus fibrillations were reviewed as biomarkers for immunotherapy treatment response. Identified were 119 immune-mediated necrotizing myopathy cases and 938 other myopathy patients. Inclusion criteria included all having electrophysiological evaluations, muscle biopsies showing inflammatory/necrotizing myopathies, comprehensively recorded neurological examinations, and creatine kinase values. Electrical myotonia was recorded in 56% (67/119) of retrospective and 67% (20/30) of our validation immune-mediated necrotizing myopathy cohorts, and significantly (P 86%) at the first visit. Inherited myopathies were commonly first suspected in them. Follow-up evaluation in patients with electrical myotonia on immunotherapy was available in 19 (median 21 months, range 2–124) which reduced from 36% (58/162) of muscles to 7% (8/121; P