COL4A4 and focal segmental glomerulosclerosis: The clinical phenotypes of heterozygous mutations in COL4A3 and COL4A4 are heterogeneous, and can cause autosomal dominant AS (ADAS), thin basement membrane nephropathy (TBMN), focal segmental glomerulosclerosis (FSGS) and benign familial hematuria (BFH) [18, 19].