Mutations in various genes have been associated with these diseases and the prototype disorder is immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) [6,7,8], caused by mutations in the Forkhead Box P3 (FOXP3) gene, leading to defective CD4+CD25+ regulatory T-cell (Treg) production and described as a Treg defect (Tregopathies; Table 2) [9]. The gene discussed is FOXP3; the disease is immune dysregulation-polyendocrinopathy-enteropathy-X-linked syndrome.