Although affected gene and type of mutation alter the ADPKD clinical phenotype (PKD1 patients have a more severe renal impairment and faster disease progression than those with PKD2 mutations; PKD1 truncating mutations result in a more severe phenotype than PKD1 non-truncating mutations), major phenotypic differences among ADPKD patients can only partly be explained by the underlying gene mutation (8–10). This evidence concerns the gene PKD2 and autosomal dominant polycystic kidney disease.