Severe combined immunodeficiency
Severe combined immunodeficiency (SCID) is the most serious human immunodeficiency disorders. It is a group of congenital disorders in which the humoral part of the patient’s immune system and cells involved in immune responses fail to work properly. Children with this horrible disorder are vulnerable to infections, retarded growth, and early death.
SCID is thought to affect between one in every 100,000 persons, and one in every 500,000 infants. Several different immune system disorders are currently grouped under SCID:
Adenosine deaminase deficiency
Bare lymphocyte syndrome
SCID with leukopenia
In order to understand why SCID is considered the most severe immunodeficiency disorder, it is helpful to have an outline of the parts of the human immune system. The cellular system is composed of many classes of T-lymphocytes (white blood cells that detect foreign invaders called antigens). The humoral system is made up of B cells, which are the only cells in the body that make antibodies. In SCID, neither one of these parts of the immune system are working properly.
SCID is an inherited disorder. For the first few months of life, a child with SCID is protected by antibodies in the mother's blood. As early as three months of age, however, the SCID child begins to suffer from many problems leading to the child becoming very weak, and after dying from an opportunistic infection.
SCID is diagnosed by the typing of T and B cells in the child's blood. B cells can be detected…