Our study, for the first time, linked a rare variant of PTPN22 to Hashimoto's thyroiditis, providing further evidence of the disease-causing or susceptibility role of PTPN22 in autoimmune thyroid disease.
A functional variant of protein tyrosine phosphatase nonreceptor 22 (PTPN22) has recently been shown to be associated with multiple autoimmune diseases, including systemic lupus erythematosus (SLE), rheumatoid arthritis, type 1 diabetes, and autoimmune thyroid disease.
HLA haplotypes DRB1*03_DQB1*02 and DRB1*04_DQB1*0302, and allelic variation of the T cell regulatory gene cytotoxic T-lymphocyte-associated antigen-4 (CTLA4) and of the T cell activation gene protein tyrosine phosphatase, non-receptor type 22 (lymphoid) (PTPN22) have been associated with type 1 diabetes and autoimmune thyroid disease.
The R620W polymorphism of the PTPN22 gene is not a major risk allele for SLE susceptibility in our sample of Caucasian individuals from northern America, the UK, or Finland, but it appears to be a risk factor for the concurrent autoimmune diseases of autoimmune thyroid disease and SLE.