Pancreatic Histopathology of Human Monogenic Diabetes Due to Causal Variants in KCNJ11, HNF1A, GATA6, and LMNA.

Context: Monogenic diabetes is thought to account for 2% of all diabetes cases, but most patients receive misdiagnoses of type 1 or type 2 diabetes. To date, little is known about the histopathological features of pancreata from patients with monogenic diabetes. Objective: Retrospective study of the JDRF Network for Pancreatic Organ Donors with Diabetes biorepository to identify possible cases of monogenic diabetes and to compare effects of genetic variants on pancreas histology. Methods: We selected cases of diabetes for genetic testing on the basis of criteria that included young age at diagnosis, low body mass index, negative autoantibody status, and/or detectable C-peptide level. Samples underwent next-generation-targeted sequencing of 140 diabetes/diabetes-related genes. Pancreas weight and histopathology were reviewed. Results: Forty-one of 140 cases of diabetes met the clinical inclusion criteria, with 38 DNA samples available. Genetic variants of probable clinical significance were found in four cases: one each in KCNJ11, HNF1A, GATA6, and LMNA. The KCNJ11 and HNF1A samples had significantly decreased pancreas weight and insulin mass similar to that of type 1 diabetes but had no insulitis. The GATA6 sample had severe pancreatic atrophy but with abundant ß cells and severe amyloidosis similar to type 2 diabetes. The LMNA sample had preserved pancreas weight and insulin mass but abnormal islet architecture and exocrine fatty infiltrates. Conclusions: Four cases of diabetes had putative causal variants in monogenic diabetes genes. This study provides further insight into the heterogeneous nature of monogenic diabetes cases that exhibited clinical and pathophysiological features that overlap with type 1/type 2 diabetes.