Association analysis of the R620W polymorphism of protein tyrosine phosphatase PTPN22 in systemic lupus erythematosus families: increased T allele frequency in systemic lupus erythematosus patients with autoimmune thyroid disease.

Objective: Recent case-control studies show associations of the minor T allele (of the C1858T single-nucleotide polymorphism corresponding to the R620W amino acid substitution) of PTPN22 with multiple autoimmune diseases, including systemic lupus erythematosus (SLE). We performed family-based association studies of this polymorphism in 4 independent cohorts containing SLE patients and their parents and/or other family members.

Methods: A total of 2,689 individuals from 902 independent Caucasian families with SLE were genotyped using polymerase chain reaction pyrosequencing (cohorts 1 and 2) and the Sequenom MassArray system (cohorts 3 and 4).