Nephronophthisis (NPHP) is an autosomal recessive, genetically heterogenic kidney disorder. Most commonly (in 20% of cases) a mutation in the NPHP1 gene is detected. The phenotype is characterized by a reduced urinary concentrating ability, corticomedullary cysts and kidney failure, with progression to end-stage renal disease before the age of 30. Three clinical cases of nephronophthisis are distinguished: infantile, juvenile and adult. Extrarenal manifestations occur in 10–20% of cases of nephronophthisis and include i.a. retinitis pigmentosa, hepatic fibrosis and bone deformities. The article comprises the cases of three children with nephronophthisis confirmed by a genetic test. The initial medical signs of the disease were anaemia and nocturnal enuresis. As a result of initial nonspecific medical signs, no or minor abnormalities detected in urine tests (a reduced urinary concentrating ability), as well as an initially normal ultrasonography examination, NPHP was diagnosed late.