Epidemiological evidence for a hereditary contribution to myasthenia gravis: a retrospective cohort study of patients from North America

Abstract

Objectives: To approximate the rate of familial myasthenia gravis and the coexistence of other autoimmune disorders in the patients and their families.

Design: Retrospective cohort study.

Setting: Clinics across North America.

Participants: The study included 1032 patients diagnosed with acetylcholine receptor antibody (AChR)-positive myasthenia gravis.

Methods: Phenotype information of 1032 patients diagnosed with AChR-positive myasthenia gravis was obtained from clinics at 14 centres across North America between January 2010 and January 2011. A critical review of the epidemiological literature on the familial rate of myasthenia gravis was also performed.

Results: Among 1032 patients, 58 (5.6%) reported a family history of myasthenia gravis. A history of autoimmune diseases was present in 26.6% of patients and in 28.4% of their family members.

Discussion: The familial rate of myasthenia gravis was higher than would be expected for a sporadic disease. Furthermore, a high proportion of patients had a personal or family history of autoimmune disease. Taken together, these findings suggest a genetic contribution to the pathogenesis of myasthenia gravis.

Keywords: epidemiology; genetics; neurogenetics; neurology; neuromuscular disease.

Conflict of interest statement

Competing interests: RJB served as a consultant for NuFactor and Momenta Pharmaceutical and receives research support from PTC Therapeutics, Ra Pharma, Orphazyme, Sanofi Genzyme, FDA OOPD, NIH and PCORI. MB reports grant support from Muscular Dystrophy Association, ALS Association, ALS Recovery Fund, Kimmelman Estate, Target ALS, Eli Lilly & Company and the National Institutes of Health (NIH) during the conduct of the study. He also reports grant support from FDA, CDC and DOD; research support from Alexion Pharmaceuticals, UCB, Cytokinetics, Neuraltus, Biogen and Orphazyme A/S; and personal fees from NMD Pharma, Ra Pharmaceuticals, Mitsubishi-Tanabe, Avexis, UCB and Denali outside the submitted work. VC served as a consultant for review and expert testimony for the Department of Health and Human Services and the Department of Justice under the Vaccine Injury and Compensation Program. Dr Chaudhry has received royalty for total neuropathy score (TNS) patented (through Johns Hopkins University) for license of TNS use from AstraZeneca, Genentech, Seattle Genetics, Calithera Biosciences, Merrimack Pharmaceuticals, Levicept, and Acetylon Pharmaceuticals. MMD serves or recently served as a consultant for ArgenX, Catalyst, CSL-Behring, Kezar, Momenta, NuFactor, RMS Medical, Sanofi Genzyme, Shire Takeda, and Spark Therapeutics. Dr Dimachkie received grants from Alexion, Alnylam Pharmaceuticals, Amicus, Biomarin, Bristol-Myers Squibb, Catalyst, CSL-Behring, FDA/OOPD, GlaxoSmithKline, Genentech, Grifols, Mitsubishi Tanabe Pharma, MDA, NIH, Novartis, Sanofi Genzyme, Octapharma, Orphazyme, Sarepta Therapeutics, Shire Takeda, Spark, UCB Biopharma, Viromed & TMA. AE was a member of the advisory board for Alexion, a scientific award jury member for Grifols and safety data monitor for UCB. MF has received honoraria for serving on advisory boards for ARGNX pharma, Alexion. MF also has research support from Catalyst, Ra pharma, Amicus, Orphazyme, Alexion, Momenta and Alnylam. JFH reports research support and grants from Alexion Pharmaceuticals, argenx BVBA, Centers for Disease Control and Prevention, Muscular Dystrophy Association, NIH (including the National Institute of Neurologic Disorders and Stroke and the National Institute of Arthritis and Musculoskeletal and Skin Disease), PCORI (Patient-Centered Outcomes Research Institute) and Ra Pharmaceuticals; and nonfinancial support from Alexion Pharmaceuticals, argenx BVBA, Ra Pharmaceuticals and Toleranzia. HJK is funded by the Muscular Dystrophy Association (508240) and by NIH grant U54NS115054; is a consultant for Alnylam Pharmaceuticals, Ra Pharmaceuticals, and UCB Pharmaceuticals; and is CEO of ARC Biotechnology, LLC, which receives support from the NIH (R41NS110331). He serves on the Editorial Board of Experimental Neurology. MMe has received honoraria as a speaker and/or moderator from Alnylam, Akcea, Pfizer and CSL Behring. She has served on Advisory Boards for Pfizer, Alnylam and Akcea. She serves as an investigator for clinical trials with Alnylam and Biogen. SM has served on advisory board meetings for Alexion and argenx. MP served on advisory board for CSL Behring, Alexion pharmaceuticals, Argenx Pharmaceuticals and has been consultant for Momenta Pharmaceuticals. DPR receives research funding from a Sponsored Research Agreement from Cabaletta Bioscience. BJT holds an American and European Union patent on the clinical testing and therapeutic intervention for the hexanucleotide repeat expansion of C9orf72, and has received research grants from The Myasthenia Gravis Foundation, the Robert Packard Center for ALS Research, the ALS Association (ALSA), the Italian Football Federation (FIGC), the Center for Disease Control and Prevention (CDC), the Muscular Dystrophy Association (MDA), Merck and Microsoft Research. BJT receives funding through the Intramural Research Program at the National Institutes of Health.

© Author(s) (or their employer(s)) 2020. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.

Figures

Figure 1

Symptom-onset age distribution of sporadic and familial cases. The density represents the relative probability of myasthenia gravis at each age point.

Figure 2

Autoimmune diseases in a cohort of 1032 patients with myasthenia gravis. (A) Occurrence of autoimmune diseases among patients with myasthenia gravis (n=275). (B) Occurrence of autoimmune diseases among familial relatives of patients with myasthenia gravis (n=293). (C) Comparisons of autoimmune diseases among patients with myasthenia gravis and among relatives. Size of each circle represents the percentage previously reported by Mao et al.