ACTN4 and focal segmental glomerulosclerosis: In the past years, many familial FSGS cases have been reported and genetic studies have identified mutations in several genes coding for proteins of the slit diaphragm complex and the podocyte which leads to autosomal recessive (NPHS1, NPHS2) or autosomal dominant (ACTN4, CD2AP, TRPC6 genes) steroid-resistant FSGS [1,4-6].