Protean appearances of immunodeficiencies: syndromes and inborn errors involving other systems which express associated primary immunodeficiency.

Developmental defects interrupting the normal evolution of immunocytes can explain many of the congenital immunodeficiency syndromes. Observations accumulated during the last decade have, however, shown that this is not the only cause, and that many diseases have signs of immunodeficiency as an accompanying feature. Severe combined immunodeficiency (SCID) is a good example of the multiple etiology of similar clinical features--they are phenocopies of a well-delineated hereditary disease. A number of recently described syndromes are reviewed, albeit an incomplete list. Metabolic disorders due to inactivity of enzymes may present characteristic ID. Some of them are explained by lack or increased need of co-enzymes (like biotin or zinc). In other syndromes, better understanding of the pathogenesis might pin down the primary failure to one single point, as shown in the hyper IgE syndrome. Other fundamental disturbances are located in the chromosome itself, eg decreased repair capacity, deletion, translocation. An attempt is made to propose a general classification accommodating all etiologic factors known to date which lead to immunodeficiency. It is obvious that within this framework the same clinical syndrome may be repeated.