Severe combined immunodeficiency disease is a congenital immunodeficiency disorder resulting in low levels of antibodies and a low number and malfunction of T lymphocytes.

Severe combined immunodeficiency disease is the most serious immunodeficiency disorder. It can be caused by several different genetic defects, most of which are hereditary. One form of the disorder is due to a deficiency of the enzyme adenosine deaminase. In the past, children with this disorder were kept in strict isolation, sometimes in a plastic tent, leading to the disorder being called "bubble boy syndrome."

Most infants with severe combined immunodeficiency disease develop pneumonia, thrush, and diarrhea, usually by age 3 months. More serious infections, including pneumocystis pneumonia, can also develop. If not treated, these children usually die before age 2.

Treatment with antibiotics and immune globulin is helpful. The best treatment is transplantation of stem cells from bone marrow or umbilical cord blood. For a deficiency of adenosine deaminase, replacement of that enzyme can be effective. Gene therapy seems to be effective in some infants who have one form of severe combined immunodeficiency disease. Gene therapy consists of removing some white blood cells from the infant, inserting a normal gene into the cells, and returning the cells to the infant.

Last full review/revision February 2003