Immunological studies in patients with juvenile-onset myasthenia gravis and in their relatives

Fifty-four patients who developed myasthenia before the age of 20 had an increased incidence of autoantibodies similar to that in adult-onset myasthenics, except that there was no significant increase of striated muscle antibodies. The increase in thyroid antibodies was associated with an increase of thyroid disease.

Their 150 relatives showed a significant increase in thyroid antibodies, in thyroid disease, and a non-significant increase in the five other autoantibodies studied. There was aggregation of thyroid antibodies in some families.

Two patients and one relative were deficient for immunoglobulins (one patient and one father for IgA and one patient for IgM).

These familial immunological abnormalities, which are more marked in the families of patients with juvenile-onset myasthenia than in the families of adult-onset patients, point to fundamental genetic immunopathogenesis of the disease.