A case of digenic maturity onset diabetes of the young with heterozygous variants in both HNF1Α and HNF1Β genes

Maturity onset diabetes of the young (MODY) is the most commonly reported form of monogenic diabetes in the pediatric population. Only a few cases of digenic MODY have been reported up to now.A female patient was diagnosed with diabetes at the age of 7 years and was treated with insulin. A strong family history of diabetes was present in the maternal side of the family. The patient also presented hypomagnesemia, glomerulocystic kidney disease and a bicornuate uterus. Genetic testing of the patient revealed that she was a double heterozygous carrier of HNF1A gene variant c.685C > T; (p.Arg229Ter) and a whole gene deletion of the HNF1B gene. Her mother was a carrier of the same HNF1A variant.Digenic inheritance of MODY pathogenic variants is probably more common than currently reported in literature. The use of Next Generation Sequencing panels in testing strategies for MODY could unmask such cases that would otherwise remain undiagnosed.