Association of the PTPN22*R620W polymorphism with autoimmune myasthenia gravis.

Objective: Our objective was to investigate a role of the intracellular tyrosine phosphatase PTPN22*R620W variant in autoimmune myasthenia gravis (MG), considering disease heterogeneity.

Methods: We used a case-control design, comparing 470 patients and 296 controls, all French whites. Patients were categorized depending on the presence of a thymoma and serum anti-titin antibodies.

Results: The 620W risk allele was increased in 293 nonthymoma patients without anti-titin antibodies (odds ratio, 1.97; 95% confidence interval, 1.32-2.97, p = 0.00059) but not in nonthymoma patients with anti-titin antibodies or in thymoma patients.

Interpretation: Our genetic findings strengthen the concept that these groups of patients correspond to etiologically distinct disease entities.