PTPN22 and celiac disease: Part of this study was presented as a poster with a title of “Polymorphism c1858t in the protein tyrosine phosphatase non-receptor type 22 in co-occurrence of type 1 diabetes and celiac disease” (Abstract Code: A-910-0012-00527) at the 43rd Annual Conference of the International Society for Pediatric and Adolescent Diabetes in Innsbruck, Austria, October 18–21, 2017.