Adenosine Deficiency- Information, Treatment & Prevention

By: Juliet Cohen

Adenosine deaminase deficiency is a ubiquitous enzyme which seems to be specially important in the evolution of thymocytes. Adenosine deaminase deficiency is very rare, but very serious, because a malfunctioning immune system leaves the body open to infection from bacteria and viruses. The disease is an autosomal recessive disease caused by receiving a deficient ADA gene from both parents. The disease is caused by a mutation in a gene on chromosome. The gene codes for the enzyme adenosine deaminase. Without this enzyme, the body is unable to break down a toxic substance called deoxyadenosine. This disease is also quite lethal, leading to death in virtually all those afflicted if not treated.

Immune deficiency in these later oncoming cases tends to be less severe, causing primarily recurrent upper respiratory and ear infections. Over time, affected individuals may develop chronic lung damage, allergies, and other health problems.

Because ADA deficiency affects the immune system, people who have the disorder are more susceptible to all kinds of infections, particularly those of the skin, respiratory system, and gastrointestinal tract. They may also be shorter than normal. Without intervention, affected individuals die from overwhelming opportunistic infections within the first few months of life. It catalyzes the deamination of adenosine and deoxyadenosine to inosine and deoxyinosine, which are converted to waste products and excreted. In the absence of functional ADA, there is an intracellular accumulation of adenosine and deoxyadenosine; these products are toxic to lymphocytes.

Bone marrow or stem cell transplants from a haploidentical donor is available for a minority of patients. Supplying the missing enzyme in this way helps some patients fight infections, while others are helped very little. The newest treatment for ADA deficiency is gene therapy. Gene therapy provides victims with their own T cells into which a normal copy of the human ADA gene has been inserted. Adenosine deaminase deficiency is the first disease to be treated with human gene therapy. Direct enzyme injections are a better method of introducing ADA to the patient. Enzyme therapy does not work for all patients. Also, in people who are treated for the disease and cured, only their somatic cells are cured, not their reproductive cells, so one's original genotype must be considered when determining the chance of passing the disease on to one's offspring. Although this disease is incurable to date, treatments are able to maintain a person so they can lead a somewhat normal life.

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