Autosomal recessive polycystic kidney disease (RPKD) (also called infantile polycystic kidney disease) and autosomal dominant polycystic kidney disease (DPKD) (or adult form) are the two main types of genetic polycystic kidney diseases (PKD) encountered in children and infants. We report here a case of DPKD with no family history and discuss the main features leading to the differential diagnosis between these two types of PKD, their prognosis and the importance of making the right diagnosis for the genetic counselling.