ADA-SCID
| Adenosine deaminase deficiency | |
|---|---|
| Classification and external resources | |
| Specialty | hematology |
| ICD-10 | D81.3 |
| ICD-9-CM | 279.2 |
| OMIM | 102700 |
| DiseasesDB | 260 |
| GeneReviews | |
Adenosine deaminase deficiency (also called ADA deficiency or ADA-SCID) is an autosomal recessivemetabolic disorder that causes immunodeficiency. It occurs in fewer than one in 100,000 live births worldwide.
It accounts for about 15% of all cases of severe combined immunodeficiency (SCID). ADA deficiency may be present in infancy, childhood, adolescence, or adulthood. Age of onset and severity is related to some 29 known genotypes associated with the disorder.
The main symptoms of ADA deficiency are pneumonia, chronic diarrhea, and widespread skin rashes. Affected children also grow much more slowly than healthy children and some have developmental delay. Most individuals with ADA deficiency are diagnosed with SCID in the first 6 months of life.
The enzyme adenosine deaminase is encoded by a gene on chromosome 20. ADA deficiency is inherited in an autosomal recessive manner. This means the defective gene responsible for the disorder is located on an autosome (chromosome 20 is an autosome), and two copies of the defective gene (one inherited from each parent) are required in order to be born with the disorder. The parents of an individual with an autosomal recessive disorder both carry one copy of the defective gene, but usually do not experience any signs or symptoms of the disorder.
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. This deficiency results in an accumulation of deoxyadenosine, which, in turn, leads to:
Because T cells undergo proliferation and development in the thymus, affected individuals typically have a small, underdeveloped thymus. As a result, the immune system is severely compromised or completely lacking.
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