The identification of variants in COL4A3, COL4A4, COL4A5, and COL4A1 in individuals displaying cystic phenotypes and chronic kidney disease (CKD) suggests that the structural and functional compromise of renal basement membranes, stemming from collagen IV variations, may predispose such individuals to cystogenesis. The gene discussed is COL4A4; the disease is chronic kidney disease.