Genetic associations between myasthenia gravis and the HL-A system.

HL-A antigens were determined in 159 myasthenic patients, 112 of whom were females and 47 males. Fifty-seven patients were thymectomized. The relationship between 23 different HL-A antigens and myasthenia gravis (MG) with reference to sex, age at onset, clinical course of MG, thymus histology, and auxiliary diseases of the patients, as well as the significance of these antigens to 245 relatives of myasthenics, were analysed. The frequencies of HL-A1 and HL-A8 were highly significantly higher in myasthenic patients than in normal Finnish controls. The increase of HL-A1 is secondary and due to a strong linkage disequilibrium between HL-A8 and HL-A1. HL-A8 appeared most often in females with onset of MG before the age of 35 years, and inpatients with thymus hyperplasia. No significant HL-A deviations were found in males or in females with later onset of disease. In seven thymoma patients the occurrence of W10 antigen was almost significantly increased.