Associated calculations for the paper "New evidence for a genetic contribution to myasthenia gravis"
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 1,032 patients diagnosed with acetylcholine receptor antibody (AChR)-positive myasthenia gravis
Methods Phenotype information of 1,032 patients diagnosed with acetylcholine receptor antibody (AChR)-positive myasthenia gravis was obtained from clinics at fourteen centers 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 1,032 patients, 58 (5.6%) reported a family history of myasthenia gravis. In comparing the familial and sporadic cohorts, the only feature that was different was the lower age of onset in familial cases. 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.