Background HNF 1B is a key factor for the normal development of the kidney and pancreas transcription. Mutations affecting the gene encoding this factor are related to different phenotypes of renal disease among glomerulocystic kidney disease (GCKD) is included.

GCKD is entity characterised by glomerular cysts with dilatation of the Bowman space and adjacent tubules.

Methods Case report: Male patient, 7 years old, with renal cystic disease prenatal diagnosis of bilateral cortical cysts distribution. Unrelated parents, mother with IgA nephropathy, no alterations of hepatic metabolism or glucose. At birth, had very enlarged kidneys with increased echogenicity and loss of cortico medullary differentiation without other extrarenal findings. The disease has slowly evolved, with increased number of cysts, always cortical distribution. No impairment of renal function, normal BP. Genetic study was performed.

Results Heterozygous mutation HNF 1B was identified (c. 1-¿_1674+del), consisting of the deletion in one of its complete gene alleles. Neither parent is a carrier of the mutation.

Conclusions The demonstration of de novo gene mutation in this patient confirms the aetiology of cystic disease.

The test is very useful because it allows early diagnosis, non-invasive, allows estimating a prognosis and genetic counselling to the family.