Severe combined immunodeficiency (SCID) due to gamma chain deficiency, also called SCID-X1, is a form of SCID characterized by severe and recurrent infections, associated with diarrhea and failure to thrive. The disease is T-B+ severe combined immunodeficiency due to gamma chain deficiency (MONDO_0010315). Also known as: SCID-X1, SCIDX1, T-B+ SCID due to gamma chain deficiency, T-B+ severe combined immunodeficiency, X-linked, X-linked severe combined immunodeficiency, XSCID, severe combined immunodeficiency, X-linked, X-linked recessive, thymic epithelial hypoplasia.