COL4A4 and Alport syndrome: Inheritance of Alport syndrome is X-linked (OMIM301050), autosomal recessive (OMIM 203780), digenic (typically with a pathogenic variant in each of COL4A3 and COL4A4 [5]) or autosomal dominant (OMIM 104200, or thin basement membrane nephropathy, due to heterozygous COL4A3 or COL4A4 variants [6]).