We report a 12-years-old Romanian boy with a diagnosis of diabetes and renal insufficiency. Mutations in homeodomain-containing transcription factor hepatocyte nuclear factor (HNF-1β) have been reported in association with maturity-onset diabetes of the young (MODY 5) and early maturity-onset diabetes, progressive non-diabetic renal dysfunction and bilateral renal cysts. We found a new heterozygous mutation in HFN-1β located in the exon 3 (c.715 G>C; p.239R) associated to pancreatic calcifications. The importance of molecular diagnosis of MODY patients is reinforced and the need for a careful follow-up is stressed in order to monitor the progression of clinical manifestations and its correlation with the gene mutation.