PTPRN and type 1 diabetes mellitus: In fact, subjects with AD have a 50% lifetime risk of additional autoimmune disease onset, thus making screening for other autoantibodies against organ-specific autoantigens (thyroid peroxidase [TPO], thyroglobulin [Tg] for AITD; insulin, glutamic acid decarboxylase-65 [GAD-65], islet antigen 2 [IA2], zinc transporter 8 [ZnT8] for T1DM; tissue transglutaminase for celiac disease; others) fundamental [3].