PKD2 and autosomal dominant polycystic kidney disease: ADPKD is classified into two types based on the mutated gene: type 1 ADPKD, caused by mutations in the PKD1 gene located on chromosome 16 (accounting for about 85% of cases), and type 2 ADPKD, caused by mutations in the PKD2 gene on chromosome 4 (present in about 15% of cases) [5,6].