Immunodeficiency and syndromes: a nosographic approach.

Immunodeficiency disorders can be classified on clinical grounds into two broad groups according to whether all features are the result of the immune defect (immunodeficiency syndromes) or whether many, even prominent, features cannot be explained by the immune defect (syndromes with immunodeficiency). X-linked agammaglobulinemia and X-linked chronic granulomatous disease are paradigmatic examples of immunodeficiency syndromes. Despite some overlap (for instance extra-immune symptoms, although minor, are present in several variants of severe combined immunodeficiency and chronic granulomatous disease) immunodeficiency syndromes and syndromes with immunodeficiency are easily distinguishable. Together with the pathogenetic classification of the WHO, the present approach to a clinical classification amplifies the operational concept of immunodeficiency also from a therapeutic point of view.