Thin basement membrane lesion is not only a collagen IV nephropathy: do not underestimate “decorative” additions to collagens

Collagen IV is the most abundant and important component of the basement membrane, a specialized form of the extracellular matrix that supports endothelial and epithelial cells in various organs. Mature collagen IV molecules are triple helices made of a combination of 3 of the 6 available α chains: α1 to α6. Among all configurations, only 3 are biochemically permissible: α1α1α2, α5α5α6, and α3α4α5. The composition of the glomerular basement membrane (GBM) starts during early development with α1α1α2 trimers and during maturation switches primarily to α3α4α5 in the glomerular tuft.