PKD2 and autosomal dominant polycystic kidney disease: Due to the allelic heterogeneity, the large size, and complex genomic structure of PKD1 and PKD2, andlack of hotspot site for mutations in these two genes, the genetic analysis of ADPKD is challenging.5PKD1 is a complex and large gene that spans 46 exons encoding polycystin-1 with 4303 amino acids.