The new guidelines [4] classify the causative genes of ADPKD into different categories: major genes (PKD1 and PKD2, the causative genes in >95% of typical ADPKD cases with a risk of kidney failure); minor genes (ALG5, ALG9, DNAJB11, GANAB, IFT140, NEK8, and PKHD1) with strong supporting data of pathogenicity; and suggested genes, for which supporting data are limited at this stage. This evidence concerns the gene ALG9 and autosomal dominant polycystic kidney disease.