HLA class II and class I polymorphism in Venezuelan patients with myasthenia gravis.

Oligotyping performed among ethnically mixed Venezuelan patients with myasthenia gravis (MG) and controls has revealed positive associations of HLA class I A31, B08, B39, B40, C15, C17, and class II DRB109 and negative associations of DQB106 and DQA102 with the disease. Sequential removal of human leukocyte antigen B (HLA-B) alleles when relative predispositional effects (RPEs) were looked for demonstrated that B08 is the allele group with the largest contribution in the overall MG patients followed by B39 and B40. Several specificities (A31, B08, C17, DRB103, DQA105, and DQB102) indicated increased frequencies among patients with thymic hyperplasia versus patients without hyperplasia or controls. Tests to identify alleles with the strongest association to MG in our patients detected DRB113 and B38 as possible predisposing secondarily associated alleles in patients with hyperplasia. The associations observed disappear after Bonferoni correction of probability values and have been described in patients of Caucasian and/or Oriental ethnic background. Thus, our results reflect the heterogeneity of our population and of the patients tested and suggest a limited influence of several HLA genes in this heterogeneous disease or that these might be only markers of nearby non-HLA genes responsible for the susceptibility or resistance effect.