The recognition of impaired immunity in children five decades ago¹,² spurred an exponential increase in knowledge of the functions of the immune system. More than 95 inherited immunodeficiency disorders have now been identified.³,⁴ Genetically determined immunodeficiency can cause not only undue susceptibility to infection but also autoimmunity and an increased risk of cancer. The defects may affect one or more components of the immune system, including T cells, B cells, natural killer cells, phagocytic cells, and complement proteins. This review will focus on molecular causes of primary immunodeficiency that affect lymphocytes.

Phenotypes

Mutations that impair the function of . . .