An ADA deficiency is a rare genetic disorder that affects the immune system and leads to severe combined immunodeficiency (SCID), or "bubble boy disease." This article covers the causes, symptoms, diagnosis, treatment, and prevention of ADA deficiency.
Causes
ADA deficiency is caused by mutations in the ADA gene, which provides instructions for producing the adenosine deaminase enzyme. By breaking down toxic byproducts of cell metabolism, such as adenosine and deoxyadenosine, this enzyme is essential. If the ADA gene is mutated, ADA activity is reduced or absent, which damages immune cells, particularly T lymphocytes. SCID is characterized by a severely compromised immune system caused by impaired immune function.
Symptoms
ADA deficiency is characterized by the following symptoms:
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A person with ADA deficiency is highly susceptible to recurrent bacterial, viral, and fungal infections, including severe and life-threatening infections.
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The failure to thrive of an infant with ADA deficiency is characterized by poor growth, weight loss, and developmental delays.
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The weakened immune system may cause chronic diarrhea due to gastrointestinal infections or inflammation.
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Infections or immune dysregulation can cause skin rashes or other dermatological abnormalities.
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It is possible for infections or immune-mediated inflammation to cause hepatomegaly (enlarged liver) and splenomegaly (enlarged spleen).
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In some cases, ADA deficiencies can lead to neurological complications such as developmental delays, intellectual disabilities, or neurologic deficits.
Diagnosis
The diagnosis of ADA deficiency involves a combination of clinical evaluation, laboratory tests, and genetic testing. Diagnostic assessments may include:
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Testing of lymphocyte counts, immune cell function, and ADA enzyme activity in blood.
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Testing for mutations in the ADA gene, confirmation of the diagnosis, and determination of the inheritance pattern of ADA deficiency.
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An assessment of the composition and function of bone marrow cells may be performed with a bone marrow biopsy in some cases.
Treatment
ADA deficiency is treated by restoring immune function, preventing infections, and improving quality of life. Options include:
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It involves administering synthetic ADA enzyme to individuals with ADA deficiency in order to compensate for the deficient or absent enzyme activity. It reduces the buildup of toxic metabolites and improves immunity.
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In the case of ADA deficiency, hematopoietic stem cell transplantation (HSCT), also known as bone marrow transplantation, may be considered a curative treatment option. The goal of HSCT is to replace the defective immune cells with healthy stem cells from a compatible donor.
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ADA gene therapy involves introducing functional ADA genes into the patient's cells to restore ADA enzyme activity and immune function.
Prevention
It is currently impossible to prevent the development of ADA deficiency because it is a genetic disorder. Families or individuals with ADA deficiency or known genetic mutations associated with the disorder may be offered genetic counseling and prenatal testing to assess the risk of recurrence in future pregnancies and provide information about testing options.
