PKD2 and autosomal dominant polycystic kidney disease: Of the four ADPKD patients with no mutation detected in PKD1, PKD2, or any cyst-pathway gene, two were at CKD stage 5 but had small atrophic kidneys (P2 and P9), one was at stage 3 with typical ADPKD features (P4), and one had very mild disease with CKD stage 1 at age 74 (P8).