WAS is a primary immunodeficiency. Many patients with WAS present with UC-like noninfectious colitis during early infancy.80 The syndrome is caused

by the absence or abnormal expression of the cytoskeletal regulator WASP and is associated with defects in most immune subsets (effector and regulatory T cells, natural killer [NK] T cells, B cells, dendritic cells, macrophages, selleck inhibitor NK cells, and neutrophils).91 In addition to features of UC, patients develop many other autoimmune complications. Allogeneic bone marrow transplantation is the standard of care for those patients.80 Patients who are not candidates for bone marrow transplantation have been successfully treated with experimental gene therapy approaches.92 and 93 Patients with atypical SCID defects have residual B- and T-cell development and oligoclonal T-cell expansion.94 VEOIBD is commonly observed in patients with atypical SCID due to hypomorphic defects in multiple genes such as DCLRE1C, ZAP70, RAG2, IL2RG, LIG4, ADA, and CD3G. 81, 82 and 95 This list of genes is likely not complete, and it

seems reasonable to assume that most genetic defects that cause T-cell atypical SCID also cause IBD. A subset of patients with SCID LBH589 purchase present with severe eczematous rash (Omenn syndrome).81 It is not clear whether residual lymphocyte function in patients with hypomorphic TTC7A mutations is a precondition for IBD or contributes to VEOIBD. 38 Intestinal and skin lesions also develop in patients

with SCID due to graft-versus-host disease in response to maternal cells. 96 Hoyeraal–Hreidarsson syndrome is a severe form of dyskeratosis congenita characterized by dysplastic nails, lacy reticular skin pigmentation, and oral leukoplakia. It is a multiorgan disorder. Patients with mutations in RTEL1 97 and 98 or DKC1 99, 100 and 101 C-X-C chemokine receptor type 7 (CXCR-7) can develop SCID and intestinal inflammation. Loss-of-function defects in IL-10 and its receptor (encoded by IL10RA and IL10RB) 102, 103, 104, 105 and 106 cause VEOIBD with perianal disease and folliculitis within the first months of life. All patients with loss-of-function mutations that prevent IL-10 signaling develop IBD-like immunopathology, indicating that these defects are a monogenic form of IBD with 100% penetrance. 106 and 107 The anti-inflammatory cytokine IL-10 is secreted by natural and induced regulatory T cells (in particular, intestinal CD4+FOXP3+ and Tr1 cells), macrophages, and B cells. Many intestinal and extraintestinal cell types express the IL-10 receptor and respond to IL-10. Defects in IL-10 receptor signaling affect the differentiation of macrophage M1/M2, shifting them toward an inflammatory phenotype.