Summary about Disease
Adenosine deaminase deficiency (ADA-SCID) is a rare, inherited metabolic disorder that severely damages the immune system, leading to severe combined immunodeficiency (SCID). This means individuals with ADA-SCID are extremely vulnerable to infections because their bodies cannot fight them effectively. ADA is an enzyme essential for breaking down toxic metabolic byproducts. When deficient, these byproducts accumulate, particularly in lymphocytes (white blood cells), disrupting their development and function.
Symptoms
Frequent and severe infections (pneumonia, sepsis, chronic diarrhea)
Failure to thrive (poor weight gain and growth)
Skin rashes
Hearing loss
Neurological problems (in some cases)
Causes
ADA-SCID is caused by mutations in the ADA gene, which provides instructions for making the adenosine deaminase enzyme. This is an autosomal recessive genetic disorder, meaning that an affected individual must inherit two copies of the mutated gene (one from each parent). If both parents are carriers of the mutated gene, there is a 25% chance their child will have ADA-SCID, a 50% chance their child will be a carrier, and a 25% chance their child will be unaffected.
Medicine Used
4. Medicine used
Enzyme replacement therapy (ERT): Involves regular injections of adenosine deaminase enzyme to help break down the toxic byproducts.
Hematopoietic stem cell transplantation (HSCT): Replacing the patient's defective immune system with healthy stem cells from a donor. This is the preferred and most effective treatment if a matched donor is available.
Gene therapy: Involves inserting a normal ADA gene into the patient's stem cells, allowing them to produce the adenosine deaminase enzyme.
Is Communicable
No, ADA-SCID is not communicable. It is a genetic disorder, not an infectious disease. It cannot be spread from person to person. The increased susceptibility to infections is a symptom of the immune deficiency, not the cause of the disease itself.
Precautions
Precautions for individuals with ADA-SCID focus on minimizing exposure to infections:
Strict hygiene practices (frequent handwashing)
Avoiding crowds and sick individuals
Vaccinations (with live vaccines generally contraindicated)
Prophylactic antibiotics and/or antiviral medications may be prescribed
Maintaining a sterile environment (especially after stem cell transplant)
How long does an outbreak last?
ADA-SCID is not an outbreak based condition. It is a chronic genetic condition. The infections experienced due to the immune deficiency will vary in duration depending on the specific pathogen and treatment effectiveness.
How is it diagnosed?
Newborn screening: Many regions include ADA deficiency in newborn screening programs, testing a blood sample for ADA enzyme activity.
Enzyme assay: Measuring the levels of adenosine deaminase enzyme in blood cells. Low or absent ADA activity indicates a deficiency.
Genetic testing: Analyzing the ADA gene for mutations.
Lymphocyte counts: Checking the number of lymphocytes (white blood cells). Individuals with ADA-SCID typically have low lymphocyte counts.
Immune function tests: Assessing the ability of the immune system to respond to infections.
Timeline of Symptoms
9. Timeline of symptoms The onset and severity of symptoms can vary.
Early infancy (within the first few months): Severe infections, failure to thrive, chronic diarrhea, skin rashes are common.
Later presentation (less common): Some individuals may have a later and milder onset, with recurring infections appearing later in childhood. Early diagnosis through new born screening helps to prevent this later presentation.
Important Considerations
Early diagnosis is crucial: Prompt diagnosis and treatment significantly improve outcomes.
Lifelong management: Treatment for ADA-SCID is often lifelong.
Genetic counseling: Important for families with a history of ADA-SCID to understand the risk of recurrence in future pregnancies.
Psychological support: The challenges of living with a severe immune deficiency can be significant, and psychological support is essential for patients and their families.