COL4A3 and Nephropathy: TBMN reported to affect at least 1% of the worldwide population is frequently associated with heterozygous mutations of COL4A3, COL4A4 or COL4A5. Although more than 1000 mutations (nearly 300 in COL4A3 and COL4A4, and 756 in COL4A5) have been identified in AS and TBMN [3], the challenges in the diagnosis of collagen IV nephropathies remain.