severe combined immunodeficiency T-B+ severe combined immunodeficiency T-B+ severe combined immunodeficiency (SCID) is a group of rare monogenic primary immunodeficiency disorders characterized by a lack of functional peripheral T lymphocytes with presence of B lymphocytes, resulting in early-onset severe respiratory viral, bacterial or fungal infections, diarrhea and failure to thrive. MEDGEN:1842847 T-cell negative B-cell positive SCID UMLS:C5679894 Editor note: add logical definition T-B+ SCID Orphanet:317416 GARD:0021405 MONDO:0044200 T+ B+ severe combined immunodeficiency