The clinical study and HLA genotyping of 112 familial myasthenia gravis patients.

One hundred and twelve cases of familial myasthenia gravis (MG) from 44 families selected from 2100 patients with MG diagnosed since 1983 in the Department of Neurology were studied. The clinical pictures and immunological features of the patients showed a great resemblance to those of sporadic cases. The pedigree analysis disclosed that the hereditary patterns of familial patients were basically Mendellian autosomal inheritance. Many predisposing factors such as fever, infection, use of aminoglycoside or vaccines, played an important role in presenting the phenotype of subclinical cases. The HLA genotyping suggested that the complement polymorphism C4A * 4, the complotype S42, and the genes 0901 and 1301 of DRB1 allele, were related to the pathogenesis of MG. It was concluded that the phenotype of MG may be the result of interaction between hereditary defects and environmental factors.