Nephrotic syndrome (NS) rarely develops before the age of 1 year. The case is presented of nephrotic syndrome occurring in the form of Denys-Drash syndrome. In a newborn of female sex in birth certificate, dysmorphia was found of the external urogenital organs. The karyotype was 46XY. Massive proteinuria, low total serum protein level, dysproteinaemia, hypercholesterolaemia justified the diagnosis of NS. In renal biopsy performed diffuse mesangial fibrosis was found. The progression of renal insufficiency was very rapid and within few weeks terminal renal failure developed. The parents refused consent to renal replacement treatment. The baby died at the age of 102 days. The autopsy examination confirmed renal changes in the form of diffuse fibrosis; gonads of testicular structure were found in the abdominal cavity.