Immunodeficiency

Abstract

Immunodeficiency is caused by failure of a component of the immune system and results in increased susceptibility to infections. The possibility of an underlying immunodeficiency should be considered if a patient has: serious, persistent, unusual, or recurrent infections; failure to thrive in infancy; known family history of immunodeficiency; unexplained lymphopenia in infancy; or a combination of clinical features characteristic of a particular immunodeficiency syndrome. The nature of the microbial infection in a particular patient provides a clue to the likely cause of immunodeficiency. Primary immunodeficiency diseases are heritable disorders that result in defects in an intrinsic component of the immune system. Secondary immunodeficiencies are caused by conditions that impair the normal function of the immune system and include viral infections, myelomatosis, non-Hodgkin’s lymphoma, severe renal or liver failure, and use of therapeutic agents which impair immunity.