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ADA-SCID: heel prick screening

Adenosine Deaminase Deficiency Severe Combined Immunodeficiency (ADA-SCID) is an inherited condition. This means that it is passed from parents to children through genes. It is very rare but it can be very serious.

It happens when a particular enzyme in your body is missing or not working. This leads to a very weak immune system.

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.

Babies born in Ireland with ADA-SCID

Around 1 in every 137,000 babies born in Ireland has ADA-SCID.

Babies with ADA-SCID inherit 1 changed gene from each parent.

How heel prick screening can help

Babies are checked for ADA-SCID as part of heel prick screening.

They are offered heel prick screening when they are around 5 days old. This test also checks for other conditions.

A midwife or nurse takes a few drops of blood from your baby's heel using a special device. If the heel-prick suggests that your baby may have ADA-SCID, they will be referred to a specialist.

Finding ADA-SCID early means treatment can start immediately.

ADA-SCID - symptoms, causes and treatment

Page last reviewed: 3 December 2025
Next review due: 3 December 2028