The R620W polymorphism in PTPN22 confers general susceptibility for the development of alopecia areata

The functional R620W (c.1858C > T) variant of the protein tyrosine phosphatase nonreceptor 22 gene (PTPN22) has been associated with a variety of autoimmune disorders. A recent study has suggested that R620W also contributes to the severe form of alopecia areata (AA). We sought to replicate the finding of an association between PTPN22 and severe AA. In addition, we wanted to study the effect of PTPN22 on the general risk to develop AA and on other subtypes of AA (mild AA, early/late age at onset, positive/negative family history). The R620W variant was genotyped in a large case-control sample of Belgian-German origin with 435 patients and 628 controls. Significant results were obtained for the overall collective of patients with AA (P = 0.007). Subdividing the sample according to severity of AA, family history and age at onset, we detected lowest P-values for patients with the severe form of AA (P-corr = 0.036), with a positive family history (P-corr = 0.042) and with an age at onset <= 20 years (P-corr = 0.048). Our results suggest the R620W variant of PTPN22 as a general risk factor in AA with the strongest effect observed among patients with a severe type of AA, a positive family history or an early onset of disease.