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Severe Combined Immunodeficiency Disease Definition
A rare, genetic immune disorder in which an infant is born with severely deficient immune capability due to the absence of leukocytes. Because the infant receives passive immunity from his or her mother at birth (and through breastfeeding), the deficiency often is not apparent until age three to six months or when the infant begins to receive routine immunizations.
Doctors may suspect SCID if there are other family members who have immunodeficiency disorders. Most often the infant’s immune status becomes suspect when there are recurrent or severe infections that a healthy immune response would accommodate. Some babies develop deep abscesses, such as in the liver. Others have chronic otitis media (middle ear infection) or sinusitis (sinus infection).
SCID Diagnosis and Treatment
Early diagnosis and treatment are essential. When doctors suspect and test for SCID within the infant’s first three months of life, a bone marrow transplantation can provide the ability to produce lymphocytes, essentially curing the immunodeficiency. Most often, however, parents and doctors do not suspect an immune problem until the child is six months to a year old. By that time other features of the immune system have developed enough to reject a bone marrow transplant unless immunoablation first destroys the child’s own bone marrow.
Bone marrow transplantation after age six months requires extended immunosuppressive therapy to allow the new blood stem cells to take root and become self cells within the body. The child may also need antibiotic prophylaxis and gammaglobulin injections to bolster the immune response until the transplant fully takes hold. Without treatment SCID is fatal by two years of age and often in the first year of life. With bone marrow transplantation the child has a good chance for normal development and a relatively healthy life.
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