Clinical and immunological differences between early and late-onset myasthenia gravis in Japan.

Immunological characteristics of myasthenia gravis (MG) with late-onset have not been fully elucidated. We examined several autoantibodies and HLA-DRB1 genotyping in 260 Japanese MG patients. Sixty-two MG patients had thymoma. The others were divided into early-onset and late-onset groups separated by an age of 50 years. The ocular form was more frequent in late-onset compared to early-onset group. Seropositivity of anti-muscle-specific tyrosine kinase antibody was 2-3% in acetylcholine receptor-seronegative patients. HLA-DRB1 genotyping failed to detect statistical differences in specific alleles between each group and healthy controls. The immunological profiles in late-onset MG were different from early-onset in Japan.