Elderly-onset familial myasthenia gravis in two siblings.

Myasthenia gravis (MG) occasionally occurs in a family, but elderly-onset (≥65 years) familial MG has been rarely reported. We here report the case of two siblings with elderly-onset MG (mean onset age: 72.5 years) and present the human leukocyte antigen (HLA) profiles (HLA-A, -B, -DR) of their family. Both patients developed generalized MG with elevated serum acetylcholine receptor antibody titers at their seventies. Of six siblings, the two patients and one unaffected sibling shared the same HLA haplotypes. Our study indicates that elderly-onset MG can occur in a family and that familial occurrence of MG may be related to certain HLA alleles.