T cell deficiency

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:

Peripheral (or non-thymic) causes of T cell deficiency include: Purine nucleoside phosphorylase deficiency, hyper IgM syndrome (in turn including, for example, 1)

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:

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. Failure to thrive and cachexia are late signs of a T-cell defect.