ACTN4 and focal segmental glomerulosclerosis: From almost 50 genes identified as causative factors of FSGS and/or SRNS, mutations in ACTN4, which encodes alpha-actinin-4, account for approximately 2% of cases, and ACTN4 is the third most common gene implicated in autosomal dominant FSGS in Europe and the United States, following INF2 (9–17%) and TRPC6 (3%) [14–17].