Different HLA DR-DQ associations in subgroups of idiopathic myasthenia gravis

We have investigated theHLA-DRB and -DQB gene polymorphism in 131 myasthenia gravis (MG) patients. TheHLA genotypes in these patients were assigned by means of restriction fragment length polymorphism (RFLP)-definedDR-DQ haplotypes, correlating to serologic HLA class II typing. Using this technique we could, among randomly selected non-thymomatous (NT)-MG patients, confirm the strong association to DR3, and 70% of the patients were found to carry a specific DR3-positiveDR-DQ haplotype,T-3.1. Furthermore, an analysis of T-3.1^– NT-MG patients revealed that 59 % were T-4.1^÷ (DR4, DQw8). Thymic hyperplasia was found in approximately 85 % of the T-3.1⁺ , as well as of the T-4.1⁺ /3.1^– patients. As previously observed, we found a clear dominance of females among the T-3.1⁺ NT-MG patients. However, among T-4.1⁺/3.1- patients, males were as common as females. Furthermore, the T-4.1⁺ patients were significantly older at the onset of disease than those who were T-3.1⁺. In female MG patients, the DRwl5-Dw2-positive haplotypeT-2.1 was strongly correlated with the presence of thymoma (T-MG). These data indicate that the HLA associations in early vs late onset of NT-MG are different, and that female patients with and without thymoma differ from each other with regard to HLA markers. Thus, at least three different HLA DR-DQ associations are found in subgroups of idiopathic MG.