COL4A3 and Alport syndrome: Additionally, subtypes of CKD can often share a phenotypic overlap with other diseases, such as Alport syndrome—the most common inherited form of glomerular CKD—which is caused by pathogenic variants in the COL4A3, COL4A4, or COL4A5 genes, and steroid-resistant nephrotic syndrome, which is associated with variants in over 40 genes.15