T cell deficiency
T cell deficiency is a deficiency of T cells, either caused by lymphocytopenia of T cells or by decreased function of individual T cells. It causes an immunodeficiency of cell-mediated immunity.
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.[1]
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).[1]
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.[1]
Secondary (or acquired) causes are mainly:[2]
- Marrow and other transplantation
- AIDS
- Cancer chemotherapy
- Lymphoma
- Glucocorticoid therapy
Overall, secondary causes are more common than primary ones.[2]
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)
Peripheral (or non-thymic) causes of T cell deficiency include: Purine nucleoside phosphorylase deficiency, hyper IgM syndrome (in turn including, for example, 1)
Effects
Pathogens of concern
The main pathogens of concern in T cell deficiencies are intracellular pathogens, including Herpes simplex virus, Mycobacterium and Listeria.[3] Also, intracellular fungal infections are also more common and severe in T cell deficiencies.[3]
Other intracellular pathogens of major concern in T cell deficiency are:
- Mycobacterium avium intracellulare[4]
- Salmonella species[4]
- Rhodococcus equi[4]
- Pneumocystis jirovecii[4]
- Toxoplasma gondii[4]
- Cryptosporidium parvum[4]
- Leishmania species[4]
- Herpesviridae, mainly herpes simplex, cytomegalovirus and varicella zoster[4]
- JC virus
- Cryptococcus neoformans[4]
- Histoplasma capsulatum[4]
- Systemic yeast infections[4]
Presentations
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.[1] Failure to thrive and cachexia are late signs of a T-cell defect.[1]
References
- 1 2 3 4 5 Medscape > T-cell Disorders. Author: Robert A Schwartz, MD, MPH; Chief Editor: Harumi Jyonouchi, MD. Updated: May 16, 2011
- 1 2 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.
- 1 2 Page 435 in: Jones, Jane; Bannister, Barbara A.; Gillespie, Stephen H. (2006). Infection: Microbiology and Management. Wiley-Blackwell. ISBN 1-4051-2665-5.
- 1 2 3 4 5 6 7 8 9 10 11 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.
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