A girl was born to two healthy individuals.

Already during the newborn screening in the maternity ward, it is discovered

that the girl has a hearing impairment. Soon, a significant kidney disorder

begins to develop, which manifests itself as nephrotic syndrome, a condition in

which large amounts of protein enter the urine. Genetic tests reveal that the

cause of these problems is an autosomal recessive form of Alport syndrome. The

cause is a mutation in type IV collagen, which is part of the basement

membranes. This problem in this syndrome is the thinning of the basement

membranes, which do not perform their function properly. In the kidney, the

result is a disruption of the filtration barrier. What parts does the

filtration barrier normally consist of?