T-B+ severe combined immunodeficiency (Monarch Disease Ontology entry MONDO_0044200) (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. Also known as: T-B+ SCID, T-cell negative B-cell positive SCID.