PTPN22 and autoimmune thyroid disease: The aim of our study was to evaluate the predisposition to autoimmune thyroiditis in patients with chronic hepatitis C virus during IFN-alpha therapy, depending on the presence of polymorphisms in the promoter region of CTLA-4C (−318)T gene and in exon 1 of A49G gene as well as C1858T transition of PTPN22 gene.