Late Diagnosis of Maturity-Onset Diabetes of the Young (MODY) 12 With Catastrophic Consequences.

Maturity-onset diabetes of the young (MODY) is a genetically and clinically heterogeneous group of diseases characterized by autosomal dominant monogenic non-ketogenic diabetes mellitus, usually with early-onset, with a prevalence of 1-5% of all diabetes cases. A 72-year-old female was admitted with intestinal occlusion, anorexia, vomiting, and weight loss for four months. Medical history of type 2 diabetes mellitus, chronic pancreatitis with abnormal pancreatic development, and acute obstructive jaundice due to a mass in the head of the pancreas with duodenum extension four months before. Assuming surgically unresectable pancreatic neoplasm, digestive bypass surgery was performed. The pathologic examination of surgical specimens was negative for neoplasm. Abdominal imaging showed the pancreatic mass, proximal bowel distension and ascites, which was negative for neoplastic cells. A percutaneous biopsy of the mass revealed adenocarcinoma. Palliative chemotherapy was started. Next-generation sequencing revealed the variant c.-8G>T in the 5' untranslated region (UTR) region of the adenosine triphosphate (ATP) binding cassette subfamily C member 8 (ABCC8) gene in heterozygosity, associated with the MODY 12 subtype. We report a possible case of MODY 12 diabetes with a phenotype not previously described: a non-neoplastic pancreatic mass that appears in a previously abnormally developed pancreas, with evolution to neoplasm along with the late development of diabetes mellitus. Although this ABCC8 gene mutation could be incidental, there could be a relationship between this mutation, pancreatic malformation, chronic pancreatitis and pancreatic neoplasm. Investigation of new phenotypes is critical, including the potential role of the ABCC8 gene in oncogenesis.