PKD1 and autosomal recessive polycystic kidney disease: In a recent study of very early onset PKD, 17% (5/30) had two hypomorphic PKD1 variants, and 30% (9/30) carried a pathogenic variant on one allele and a likely hypomorphic variant on the other allele of the PKD1 gene, demonstrating a clear mechanism for early onset ARPKD dues to biallelic PKD1 variants [34].