PKD1 and cystic kidney disease: <h4>Background</h4>Autosomal dominant polycystic kidney disease (ADPKD) is characterized by renal cyst formation due to mutations in genes coding for polycystin-1 [PKD1 (85-90% of cases), on ch 16p13.3] and polycystin-2 [PKD2 (10-15% of cases), on ch 4q13-23] and PKD3 gene (gene unmapped).