Adenosine Deaminase Deficiency Severe Combined Immunodeficiency (ADA-SCID) is an inherited disease. This means you are born with it. It is very rare but it can be very serious.
ADA-SCID is caused by a lack of adenosine deaminase (ADA). This is an enzyme that helps to break down toxins in our body’s cells.
Our immune system protects us from infections. Babies born with ADA-SCID have a weak immune system, so they cannot fight off infections. This means that common infections could be life-threatening for them.
Diagnosing ADA-SCID
At around 5 days old, your baby will be offered heel prick screening to check for ADA-SCID. This involves pricking your baby's heel to collect drops of blood to test.
If ADA-SCID is diagnosed, your baby is at risk of severe life-threatening infections and other complications. This can be avoided with early diagnosis and the correct treatment.
Symptoms of ADA-SCID
Early symptoms in babies under 6 months include:
- frequent, severe infections, such as chronic diarrhoea or pneumonia
- slower growth and development than most children
- issues with their bones - for example, unusual rib-ends that may be seen on an x-ray of their chest
- breathing difficulties
As children grow older, symptoms can include:
- slow development of the central nervous system
- hearing problems - some children may lose their hearing over time
- learning and behavioural difficulties
- problems with organs such as their liver, kidneys or lungs
Treating ADA-SCID
Patients diagnosed with ADA-SCID will start on enzyme replacement therapy (ERT).
Enzyme replacement therapy corrects the ADA and adenosine levels in the blood. This usually leads to improved immune function.
Patients are also given treatments to protect them from severe infection, such as antibiotics and immunoglobulin replacement therapy. This combination of treatments can help keep the patient safe until they can get long-term treatment.
Long-term treatment options include:
- haematopoietic stem cell transplantation (HSCT)
- gene therapy
You need to travel abroad for HSCT and gene therapy.
How ADA-SCID is inherited
ADA-SCID is caused by changes (mutations) in the ADA gene, which result in no or very low levels of the enzyme ADA.
Enzymes are protein substances that help speed up chemical reactions in the body.
If the body does not have enough of the ADA enzyme, a toxic substance called deoxyadenosine builds up. This stops cells from dividing properly. It makes it harder for the body to fight infections.
Both parents usually carry a copy of the gene. Their children have a 1 in 4 chance of being affected.