Immunodeficiency disorders

Disorders in which there is a failure of the immune system’s defences to fight infection and tumours. They may be due to an inherited or a congenital defect or may be the result of acquired disease. The result is persistent or recurrent infection, including those with organisms that would not ordinarily cause disease, and an undue susceptibility to certain forms of cancer. The infections in people with immunodeficiency disorders are sometimes called opportunistic infections; examples include pneumocystic pneumonia, fungal infections, and widespread herpes simplex infections. Congenital or inherited deficiencies can occur in either of the 2 prongs of the adaptive immune system: humoral or cellular. Deficiencies of the humoral system include hypogammaglobulinaemia and agammaglobulinaemia. The former may cause few or no symptoms, depending on the severity of the deficiency, but agammaglobulinaemia can be fatal if not treated with immunoglobulin. Congenital deficiencies of T- lymphocytes may lead to problems such as persistent and widespread candidiasis (thrush). A combined deficiency of both humoral and cellular components of the immune system, called severe combined immunodeficiency (SCID), is usually fatal in the 1st year of life unless treatment can be given by bone marrow transplant. Acquired immunodeficiency may be due either to disease processes (such as infection with HIV, which leads to AIDS) or damage to the immune system as a result of its suppression by drugs. Severe malnutrition and many cancers can also cause immunodeficiency. Mild immunodeficiency arises through a natural decline in immune defences with age.