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