Myasthenia gravis patients with thymus hyperplasia and myasthenia gravis patients with thymoma display different HLA associations.

Thirty myasthenia gravis (MG) patients (9 with thymoma, 12 with thymus hyperplasia and 9 with thymic atrophy) and 181 Norwegian healthy controls were serologically typed for HLA-A, -B and -DR antigens and genomically typed for HLA-DQA1 and HLA-DQB1 alleles by probing in vitro amplified DNA with sequence-specific oligonucleotides. In patients with thymus hyperplasia the frequency of the DQB1*0201 allele was increased compared to controls (RR = 3.5, p less than 0.05), whereas among the patients with thymoma this allele was not observed (RR = 0.06, p less than 0.01). The frequencies of HLA-B8, -DR3 and -DQA1*0501, which are in strong linkage disequilibrium with DQB1*0201, were increased in patients with hyperplasia and reduced in patients with thymoma. The data suggest that different HLA genes predispose to two different forms of MG.