Any focal segmental glomerulosclerosis in which the cause of the disease is a mutation in the ACTN4 gene. The disease is Monarch Disease Ontology entry MONDO_0011303 (focal segmental glomerulosclerosis 1). Also known as: ACTN4 focal segmental glomerulosclerosis, FSGS1, familial idiopathic steroid-resistant nephrotic syndrome with focal segmental glomerulosclerosis, focal segmental glomerulosclerosis caused by mutation in ACTN4, focal segmental glomerulosclerosis type 1.