Type 1 autoimmune pancreatitis (IgG4-related disease) presenting as new-onset diabetes mellitus: a case report

BACKGROUND: Type 1 autoimmune pancreatitis (AIP) is the pancreatic manifestation of IgG4-related disease (IgG4-RD) and is an uncommon cause of diabetes mellitus. CASE PRESENTATION: Here, we report the case of a 65-year-old white Australian man who was diagnosed with diabetes mellitus secondary to possible IgG4-related disease and had a good clinical and radiological response to corticosteroid therapy. CONCLUSIONS: This case report highlights that IgG4-related disease should be considered in patients who present with acute hyperglycemia, have negative GAD and IA2 antibody status and lack features of insulin resistance. Furthermore, corticosteroid therapy can lead to an improvement in glycemic control in patients with diabetes mellitus secondary to IgG4-related disease.