<unk> , or ADA deficiency, is an inherited immunodeficiency syndrome accounting for about 15% of all cases of severe combined immunodeficiency (SCID). This disease is due to a lack of the enzyme<unk><unk>  coded for by a gene on chromosome 20. There is an accumulation of dATP, which causes an increase in S-adenosylhomocysteine; both substances are toxic to immature lymphoid cells, so fail to reach maturity. As a result, the immune system of the afflicted person is severely compromised or completely lacking. The enzyme<unk><unk>  is important for purine metabolism.
Adenosine deaminase deficiency
Carbamoyl phosphate synthetase I deficiency
Triosephosphate isomerase deficiency
Ornithine translocase deficiency
Pyruvate kinase deficiency
ALA dehydratase deficiency
Pyridoxamine 5-prime-phosphate oxidase deficiency
Purine nucleoside phosphorylase deficiency