Pathogenic Variants in the Genes Affected in Alport Syndrome (COL4A3-COL4A5) and Their Association With Other Kidney Conditions: A Review

Massively parallel sequencing identifies pathogenic variants in the genes affected in Alport syndrome (COL4A3-COL4A5) in as many as 30% of individuals with focal and segmental glomerulosclerosis (FSGS), 10% of those with kidney failure of unknown cause, and 20% with familial immunoglobulin A (IgA) glomerulonephritis. FSGS associated with COL4A3-COL4A5 variants is usually present by the onset of kidney failure and may develop because the abnormal glomerular membranes result in podocyte loss and secondary hyperfiltration. The association of COL4A3-COL4A5 variants with kidney failure or IgA glomerulonephritis may be coincidental. However, pathogenic variants in these conditions occur more often than they should by chance, which suggests that the variants are disease causing. COL4A3-COL4A5 variants are also found in cystic kidney diseases after autosomal dominant polycystic kidney disease has been excluded. COL4A3-COL4A5 variants should be suspected in individuals with FSGS, kidney failure of unknown cause, or familial IgA glomerulonephritis, especially where there is persistent hematuria and a family history of hematuria or kidney failure.

Automated summary

Massively parallel sequencing can identify pathogenic variants in the genes affected in Alport syndrome (COL4A3-COL4A5), with these variants being present in up to 30% of individuals with FSGS and other kidney diseases. FSGS associated with COL4A3-COL4A5 variants typically manifests before the onset of kidney failure and may result from abnormal glomerular membranes. However, COL4A3-COL4A5 variants may also be coincidental with kidney failure or IgA glomerulonephritis.