Recently, in a minor subset of patients, in whom ADPKD manifests very early in life and presents as a much more severe disorder2 it was demonstrated that early and severe ADPKD is not strictly confined to individuals with a PKD1 variant as previously thought but can also occur in other genetic combinations: patients with a PKD2 variant3, coinheritance in trans of an incompletely penetrant PKD1 allele with an inactivating PKD1 variant4. This evidence concerns the gene PKD1 and autosomal dominant polycystic kidney disease.