During the preclinical phase, this autoimmune process is marked by circulating auto-antibodies against pancreatic islets or against beta cell antigens, such as islet cell antibodies (ICA), glutamic decarboxylase antibodies (GADA, recently replaced by the anti-GAD65, more specific for Type 1 diabetes), protein tyrosine phosphatase ICA 512 (IA2) antibodies (anti-IA2), and auto-antibodies to Insulin (IAA). Here, PTPRN is linked to type 1 diabetes mellitus.