FOXP3 and immune dysregulation-polyendocrinopathy-enteropathy-X-linked syndrome: In IPEX, the lack of or mutant FOXP3 protein causes abnormal Treg function, which causes systemic autoimmunity and severe enteropathy associated with eosinophilic inflammation.121 Mutations in CD25 encoding IL2RA, a protein constituting the high affinity IL‐2 receptor results in an IPEX‐like syndrome.