ADA

About ADA

ADA on chromosome 20q13.12 encodes adenosine deaminase, an enzyme of purine metabolism that converts adenosine and deoxyadenosine into inosine and deoxyinosine. When the enzyme is missing, toxic deoxyadenosine metabolites accumulate and are particularly damaging to developing lymphocytes. Variants on both copies of the gene cause ADA deficiency, a form of severe combined immunodeficiency in which affected infants have very low numbers of T, B, and NK cells and suffer serious infections, and which can also affect other organs. ADA deficiency has an important place in the history of medicine: in 1990 a four year old girl with the condition received the first approved gene therapy trial treatment in the United States at the National Institutes of Health. Treatment options include hematopoietic stem cell transplantation, enzyme replacement therapy with pegylated ADA, and gene therapy using modified stem cells taken from the patient, approved in Europe as Strimvelis in 2016.