Autoimmunity in myasthenia gravis: a family study.

The prevalence of autoantibodies to muscle, epithelial cells of calf thymus, thyroid, gastric parietal cells and antinuclear and rheumatoid factors has been studied in the sera of thirty-two patients with myasthenia gravis and their relatives. Previous reports of an increased prevalence of autoantibodies in the sera of patients with myasthenia gravis have been confirmed and it has been shown that concurrent reactivity to muscle and thymus is closely correlated with the severity of the myasthenia and the presence of a thymoma, whereas no such correlation occurred with the other antibodies studied. None of the sera from relatives or spouses showed concurrent reactivity with thymus and muscle, and with the exception of one patient with pernicious anaemia, sera from patients with a variety of other diseases were also negative. A slight increase in the prevalence of autoantibodies to thyroid and gastric components and antinuclear factor was found in first degree relatives of patients with myasthenia gravis; this could be accounted for by their aggregation in a few families.