Genetic Variants of the COL4A3, COL4A4, and COL4A5 Genes Contribute to Thinned Glomerular Basement Membrane Lesions in Sporadic IgA Nephropathy Patients

Thinned glomerular basement membrane (tGBM) lesions are not uncommon in IgA nephropathy (IgAN). Type IV collagen-built of α 3, α 4, and α 5 chains, encoded by COL4A3 / COL4A4 / COL4A5 genes-is the major component of glomerular basement membrane (GBM). In recent years, mutations in type IV collagen-encoding genes were also reported in patients with a histologic diagnosis of FSGS. Pathogenic COL4A3 / COL4A4 / COL4A5 variants were recently identified in familial cases of IgAN, but the contribution of these variants to sporadic IgAN is still unclear.