T cell deficiency
Classifications of causes
By complete versus partial deficiency
Complete insufficiency of T cell function can result from hereditary conditions (also called primary conditions) such as severe combined immunodeficiency (SCID), Omenn syndrome, and Cartilage-hair hypoplasia.
Causes of partial insufficiencies of T cell function include acquired immune deficiency syndrome (AIDS), and hereditary conditions such as DiGeorge syndrome (DGS), chromosomal breakage syndromes (CBSs), and B-cell and T-cell combined disorders such as ataxia telangiectasia (AT) and Wiskott-Aldrich syndrome (WAS).
Primary versus secondary
Primary (or hereditary) immunodeficiencies of T cells include some that cause complete insufficiency of T cells, such as severe combined immunodeficiency (SCID), Omenn syndrome, and Cartilage-hair hypoplasia.
Secondary (or acquired) causes are mainly:
Overall, secondary causes are more common than primary ones.
Thymic versus peripheral
Causes of T cell deficiency by thymic hypoplasia can, in turn, be classified as:
- hypoparathyroid (such as Di George's syndrome)
- euparathyroid (Such as Nezelof syndrome and Ataxia telangiectasia)
Pathogens of concern
The main pathogens of concern in T cell deficiencies are intracellular pathogens, including Herpes simplex virus, Mycobacterium and Listeria. Also, intracellular fungal infections are also more common and severe in T cell deficiencies.
Other intracellular pathogens of major concern in T cell deficiency are:
- Mycobacterium avium intracellulare
- Salmonella species
- Rhodococcus equi
- Pneumocystis jirovecii
- Toxoplasma gondii
- Cryptosporidium parvum
- Leishmania species
- Herpesviridae, mainly herpes simplex, cytomegalovirus and varicella zoster
- JC virus
- Cryptococcus neoformans
- Histoplasma capsulatum
- Systemic yeast infections
Presentations differ among causes, but T cell insufficiency generally manifests as unusually severe common viral infections (e.g. by respiratory syncytial virus (RSV), enterovirus, rotavirus), mucocutaneous candidiasis, diarrhea, and eczematous or erythrodermatous rashes. Failure to thrive and cachexia are late signs of a T-cell defect.
- Medscape > T-cell Disorders. Author: Robert A Schwartz, MD, MPH; Chief Editor: Harumi Jyonouchi, MD. Updated: May 16, 2011
- Page 432, Chapter 22, Table 22.1 in: Jones, Jane; Bannister, Barbara A.; Gillespie, Stephen H. (2006). Infection: Microbiology and Management. Wiley-Blackwell. ISBN 1-4051-2665-5.
- Page 435 in: Jones, Jane; Bannister, Barbara A.; Gillespie, Stephen H. (2006). Infection: Microbiology and Management. Wiley-Blackwell. ISBN 1-4051-2665-5.