As with IPEX patients, Foxp3 deficiency causes an absence of functional Foxp3+ Tregs, leading to multiorgan lymphoid and myeloid infiltration with systemic autoimmune manifestations comparable to those of IPEX in human [1, 4, 25]. The gene discussed is FOXP3; the disease is immune dysregulation-polyendocrinopathy-enteropathy-X-linked syndrome.