In addition to “classic IPEX”, a group of patients with an IPEX- like phenotype without pathological variant in FOXP3 gene emerged, and several genes, such as IL2RA, STAT5b, GOF in STAT1/3, LRBA and CTLA4, have been identified as causative genes for IPEX-like phenotype. This evidence concerns the gene STAT5B and immune dysregulation-polyendocrinopathy-enteropathy-X-linked syndrome.