PKD2 and chronic kidney disease: In another study from the Columbia University group, where one of the largest cohorts was sequenced, including 3315 patients affected by CKD, Groopmanan et al. identified monogenic disorders in 10% of the cohort, of those, about 100 patients, accounting for 30% of the diagnostic yield, showed mutations in COL4A3, COL4A4, or COL4A5. This study demonstrated that collagen IV variants were the second most frequent genetic disorders in the CKD cohort, after the 31% of PKD1 and PKD2 pathogenic variants.