T Cell Deficiency

T cell deficiency, also called as cell-mediated immune deficiency, accounts for 5-10% of all primary immune deficiency diseases. This form of immune deficiency is characterized by reduced number of peripheral blood T cell and/or reduced proliferative response to mitogens. Patients are predisposed to recurrent, severe infections, failure to thrive, and chronic diarrhea. Inclusion of T cell receptor circles (TREC) in newborn screen at birth has facilitated early identification of T cell lymphopenia. Early diagnosis and treatment via immune reconstitution are essential for survival in such patients. Patients with life-threatening T cell deficiency are often maintained on antimicrobial prophylaxis to prevent opportunistic infections. Severe combined immune deficiency (SCID) and DiGeorge Syndrome (DGS) are prototype of primary T cell immunodeficiency diseases and will be our primary discussion in this chapter. We will start with cases of T cell immunodeficiency disorders and discuss the diseases in detail including clinical presentation, diagnosis, and management.