Familial myasthenia gravis: a study of three families.

Six patients suffering from familial myasthenia gravis belonging to three different families are described. Three brothers are classified as having familial limb-girdle myasthenia and the other three patients, belonging to two other families, are classified as having familial congenital myasthenia. The clinical features, HLA antigen typing, autoantibody screening and anti-acetylcholine receptor antibodies were analysed. The variability of this condition from family to family is exemplified in this series and confirms the heterogeneous nature of familial myasthenia gravis.