Myasthenia gravis occurring in families

Abstract

The forms and features of myasthenia gravis occurring in families have been reviewed and 6 additional families are reported. Two additional sibships, the 1 occurring in infancy and childhood and the other coming on in adulthood, both without parental involvement are also presented. A father contracting myasthenia gravis in adulthood and his son acquiring it in childhood are also reported with a study of the mother and 4 uninvolved siblings. Fortuitous supramanubrial thymectomy in the son during tracheostomy for crisis is described. Three instances of myasthenia gravis occurring in more distant relationships are presented. The occurrence of myasthenia gravis in families is more common than can be explained by mere probability. The present available information concerning family aggregates and twin studies of myasthenia is inadequate to clearly support genetic mechanisms as determinants though the evidence cannot entirely exclude them. The possibility of exposure to a common factor(s) at an early age in the environment is suggested as a cause for myasthenia gravis such as a chronic low-grade viral infection.