Besides insulitis, which has been shown to be present in 70% of newly diagnosed T1D patients [28], T1D has also for long been associated with presence of autoantibodies against islet cells (ICA), insulin (IAA), the 65 kDa isoform of glutamic acid decarboxylase (GAD65), and the two tyrosine phosphatase proteins ICA512 (IA-2) and Phogrin [2]. Here, PTPRN2 is linked to type 1 diabetes mellitus.