A homozygous truncating mutation within the C-terminal NC1 domain of COL4A4 has previously been reported in association with autosomal recessive Alport syndrome, but the phenotype of the obligate carrier parents was not documented in this report [28], so it is not known whether this similar mutation in a different type IV collagen chain in heterozygosity has similar phenotypic effects to the mutation described here. This evidence concerns the gene COL4A4 and autosomal recessive Alport syndrome.