ada deficiency

Adenosine deaminase deficiency

Adenosine deaminase deficiency, also called ADA deficiency or ADA-SCID, is an autosomal recessive metabolic disorder that causes immunodeficiency.

It accounts for about 15% of all cases of severe combined immunodeficiency (SCID).

ADA deficiency may present in infancy, childhood, adolescense, or adulthood. Age of onset and severity is related to some 29 known genotypes associated with the disorder.


ADA deficiency is due to a lack of the enzyme adenosine deaminase coded for by a gene on chromosome 20. There is an accumulation of deoxyadenosine, which causes an increase in S-adenosylhomocysteine; both substances are toxic to immature lymphocytes, which thus fail to mature. As a result, the immune system is severely compromised or completely lacking.

The enzyme adenosine deaminase is important in the purine salvage pathway.


Treatments include:

On September 14, 1990,the first gene therapy to combat this disease was performed by Dr. W. French Anderson on a four year old girl, Ashanti DeSilva, at the National Institutes of Health, Bethesda, Maryland, U.S.A.


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