For long-time, combination screenings of autoantibodies (Abs) directed against insulin (IAA), proinsulin, glutamic acid decarboxylase (GAD) isoforms GAD65, GAD67, the insulinoma-associated antigen (IA-2)/tyrosine phosphatase-like molecule IA-2 β [4] have represented the mainstay for classifying diabetes as autoimmune-mediated and for stratifying risk in first-degree relatives [5]. Here, PTPRN is linked to diabetes mellitus.