By testing autoantibodies, using a Type 1 diabetes genetic risk score and sequencing of all known monogenic diabetes genes in an unselected paediatric diabetes cohort, we aimed to determine whether triple antibody testing (GAD, IA2 and ZnT8) and the Type 1 diabetes genetic risk score could distinguish monogenic diabetes from Type 1 diabetes in the Iranian population where >30% of marriages are consanguineous 18, 19, 20. Here, PTPRN is linked to type 1 diabetes mellitus.