The International Union of Immunological Societies (IUIS) Primary Immunodeficiency Diseases (PID) Classification Committee

Primary immune deficiency diseases (PID) comprise a genetically heterogeneous group of disorders that affect distinct components of the innate and adaptive immune system, such as neutrophils, macrophages, dendritic cells, complement proteins, NK cells, as well as T and B lymphocytes. The study of these diseases has provided essential insights into the functioning of the immune system. Over 120 distinct genes have been identified, whose abnormalities account for more than 150 different forms of PID. The complexity of the genetic, immunological, and clinical features of PID has prompted the need for their classification, with the ultimate goal of facilitating diagnosis and treatment. To serve this goal, an international Committee of experts has met every two years since 1970. In its last meeting in Jackson Hole, Wyoming, United States, following three days of intense scientific presentations and discussions, the Committee has updated the classification of PID as reported in this article.