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Newborn Screening Ontario
Screening Results

Severe Combined Immune Deficiency (SCID)Download version for offline viewing or printing
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At a Glance

Approximate Incidence in Ontario

1 in 50,000-100,000

Marker Measured

T-Cell Receptor Excision Circles (TRECs)

Screening can Prevent

Severe and life-threatening infections

Treatment

Medications, bone marrow transplant, enzyme replacement therapy, gene therapy

  • Screening is Important
    • In Ontario, a heel prick is used to take a few drops of blood from each baby shortly after birth. The blood is tested for 29 treatable diseases, including Severe Combined Immune Deficiency (SCID).
    • A screen positive result means that more tests are needed to know whether or not a baby has SCID. It does not mean that a baby has SCID. Babies identified at a young age through screening can be treated early to help prevent health problems
  • What is SCID?

    Severe Combined Immune Deficiency (SCID) is a group of rare, inherited (genetic) diseases that affect the immune system, the body’s natural defense against infections.

    • Babies with SCID are missing important immune cells.
    • These babies are at risk for many infections which could become fatal.
    • SCID is not contagious.

    If diagnosed early

    • Treatments exist to help and sometimes cure children with SCID before they become ill.
    • These treatments can save the baby’s life.
  • Screening Positive for SCID
    • It is normal for parents and guardians to feel worried when their baby has a screen positive result. A ‘screen positive’ result does not mean that a baby has SCID. It means that there is a chance that the baby may have SCID.
    • Follow-up testing is important to find out whether the baby truly has SCID.
    • The baby’s health care provider or a health care provider at a newborn screening Regional Treatment Centre will discuss the results with the baby’s family.
    • Follow-up blood tests are arranged as soon as possible.
    • It can take a few days to weeks to find out if a baby truly has SCID or not. This waiting period can be hard for families. Families may be given special instructions to follow during this waiting period.
  • Possible Follow-up Test Results
    • Normal – the baby does not have SCID.
    • Abnormal – the baby does have SCID and will need treatment. The family will be supported by a team of caring specialists. Testing will be needed to determine the specific type of SCID.
    • Inconclusive – more testing is required. The baby will be followed closely by an immunologist (an immune system specialist) to ensure that he/she receives optimal care. Sometimes babies are found to have other conditions which cause an immune deficiency as one of their symptoms.
  • Signs and Symptoms

    Babies with SCID are protected by their mother’s immune system for a little while after birth. Screening can detect SCID before symptoms appear.

    Without treatment, early signs of the disease begin in the first months of life and can include:

    • poor growth
    • diarrhea
    • frequent infections
      • ear infections
      • lung infections
      • thrush (a fungal infection in the throat)
      • infections that do not go away with treatment

    Early treatment helps to prevent serious and life-threatening infections such as:

    • pneumonia (lung infection)
    • meningitis (infection of the brain lining)
    • sepsis (blood infection)
  • Treatment

    1) Bone Marrow Transplant
    Immune cells are made in the bone marrow. The most common and effective treatment for SCID is a bone marrow transplant from a person with a healthy immune system. A sibling donor is the best option, but parents or unrelated donor may be used.

    • This replaces the baby’s immune system with a healthy immune system.
    • Bone marrow transplantation can cure SCID.
    • There is a high chance of success if the transplant is done in the first months of life while the baby is healthy.
    • A healthy donor can re-grow the bone marrow cells that they donated.

    2) Short-Term Therapies

    These therapies may be necessary until a bone marrow transplant can be done.

    • Isolation
      • Limiting contact with people, especially young children, to avoid catching infections.
    • Antibiotics
      • Antibiotics can prevent and treat infections
    • Antibody therapy
      • Antibodies are proteins made by the immune system that help fight infections.
      • Babies with SCID cannot make their own antibodies.
      • Antibody injections can help protect babies with SCID and provide them with some protection against common infections.
    • Avoid Live Vaccines
      • Certain vaccines (especially rotavirus, measles, mumps, rubella and varicella) cannot be given until the baby has a working immune system.
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    3) Other Therapies

    Some types of SCID have different treatment options such as enzyme replacement therapy and gene therapy. These will be offered by the immunologist, if available.

  • Living with SCID
    • With screening and early treatment, most babies with SCID will be able to lead normal healthy lives.
    • Babies are less likely to develop life-threatening infections when treatment starts early.
    • A bone marrow transplant in the first months of life, while the baby is healthy, has a very high rate of success.