PTPRN and type 1 diabetes mellitus: Positivity for two or more islet autoantibodies against insulin (IAA), glutamic acid decarboxylase 65 (GAD65), tyrosine phosphatase-related islet antigen-2 (IA-2), islet cell autoantigen (ICA), or zinc transporter 8 (ZnT8) confers a >80% risk of developing T1D within 20 years and is used together with glycemia data for the classification of T1D into disease stages [3,4,24].