A novel splice-site mutation of the HNF1B gene in a family with maturity onset diabetes of the young type 5 (MODY5).

SUMMARY

Maturity-onset diabetes of the young (MODY) is a form of monogenic diabetes mellitus characterised by early onset and dominant inheritance. Delayed diagnosis or misdiagnosis as type 1 or type 2 diabetes mellitus is common. Definitive genetic diagnosis is essential for appropriate treatment of patients with MODY. The hepatocyte nuclear factor 1-beta (HNF1B) gene is responsible for MODY type 5 (MODY5), which has distinctive clinical features including renal disease. MODY5 should always be considered by clinicians in patients with early onset diabetes and renal anomalies. We report a case of a 30-year-old Japanese male with early-onset diabetes mellitus, renal anomalies and family history of diabetes that was suggestive of MODY5. Renal histology showed no evidence of diabetic nephropathy. Genetic testing revealed a novel heterozygous splice-site mutation of the HNF1B gene in the family members. It was strongly suggested that the mutation could underlie our patient's MODY5.

LEARNING POINTS

Genetic diagnosis of MODY is relevant for appropriate treatment. Dominantly inherited early-onset diabetes mellitus with renal cysts suggests MODY5. Scanning the non-coding regions is important for not missing a mutation in HNF1B.