Prenatal diagnosis of HNF1b mutation allows recognition of neonatal dysglycemia.

Maturity onset diabetes of the young (MODY) is the most common form of monogenic diabetes in Europe, affecting between 1 and 6% of diabetic patients. It comprises a group of heterogeneous genetic disorders characterized by early onset of diabetes (commonly before age 25), absence of autoimmunity, and beta-cell dysfunction. So far, mutations in 14 different genes involved in glucose homeostasis and pancreatic development [1] have been associated with this disease. Although it is an autosomal dominant disorder, de novo mutations should be taken into consideration in patients without a family history of diabetes. Most cases of MODY are due to mutations in GCK, HNF1a, HNF4a and HNF1b, previously known as MODY2, MODY3, MODY1, and MODY5, respectively. Among these, HNF1b is an active transcription factor that forms homodimers or heterodimers with HNF1a and plays a fundamental role in kidney development, nephron differentiation, and pancreatic growth and differentiation. Mutations in this gene lead to congenital anomalies of the kidney and urinary tract, genital malformations, pancreatic atrophy with endocrine and exocrine deficiency [2]. Diabetes usually onsets in early adulthood and frequently requires insulin treatment. We present an unusual case of a prenatal diagnosis that revealed a mutation in the HNF1b gene responsible for neonatal hyperglycemia in a pregnant woman affected by X-linked ectodermal dysplasia.