T-lymphocyte immunodeficiencies are the most severe forms of primary immunodeficiencies (PID) because T cells are central in the induction of antigen-specific immune responses. It is estimated that they represent approximately 20% of all types of PID.<sup>97 Primary immunodeficiency disease Report of a WHO scientific group Clin Exp Immunol 1997 ;  109 (suppl 1) : 1-28

Cliquez ici pour aller à la section Références</sup> A large number of distinct phenotypes of T-cell immunodeficiencies have been reported. Molecular diagnosis is now possible for many because disease gene identification has been provided in many cases. It is now possible to connect a phenotype and a genotype better, which sometimes leads to understanding the disease mechanism.