COL4A3 and Microscopic hematuria: Some heterozygous mutations in COL4A3 and COL4A4 genes can cause a milder phenotype, defined as thin basement membrane nephropathy (TBMN; MIM#141200, or benign familial hematuria), which is characterized by persistent microscopic hematuria although rarely combined with progressive proteinuria and end-stage renal disease [4].