Severe Combined Immunodeficiency (SCID) | Diagnosis and Treatment

How is severe combined immunodeficiency diagnosed?

A diagnosis of severe combined immunodeficiency (SCID) is usually based on a complete medical history and physical examination of your child. In addition, multiple blood tests — including a complete blood cell count — may be ordered to help confirm the diagnosis. 

Newborn screening also plays an important role in detecting SCID before symptoms emerge. A growing number of states test for SCID as part of a mandated newborn screening process. Having a screening performed is especially important, because many infants with SCID show no signs until they actually develop an infection.

Screening does have its limitations. A positive result for SCID on a newborn screen is not the same as a conclusive diagnosis, and screening does not catch all children with SCID and SCID variants. However, it is an important means by which children who may have SCID can be detected early.

What are the treatment options for SCID?

Guarding against infection

Nothing is more important to the health of a child with SCID than warding off potential infections. Your child's clinician can advise you about the exact steps you should be taking to help reduce the risk of infection.

Mothers of newborn children with SCID should discuss the pros and cons of breastfeeding with their clinicians, as some infections can be passed through breast milk.

As a rule, children with SCID should not receive the standard childhood vaccinations. Because the B cells of children with SCID do not function properly, their bodies can't produce the normal antibodies that fight off viruses. Since many vaccines are actually live viruses, they pose too high a risk of infection to be safe for a child with a drastically weakened immune system.

Other ways to avoid potential infections include basic precautions such as:

  • keep your child away from crowds, dirty places or anyone who is ill or seems to be "coming down with something"
  • follow a strict hand washing regimen for your child, your family and any visitors
  • use protective face masks at the recommendation of your child's doctor
  • give your child antibiotics, antifungal or antiviral medications at the direction of your child's doctor

Antibody infusions

Because your child's body does not have healthy B cells that produce antibodies against infection, he or she may need regular intravenous (IV, administration through a vein) or subcutaneous infusions (administration under the skin) of the antibody immunoglobin (also known as immune globin, gammaglobin, IVIG or SCIG).

Stem cell/bone marrow transplants

Nearly every child with SCID is treated with a stem cell transplant, also known as a bone marrow transplant. This is the only available treatment option that has a chance of providing a permanent cure. The bone marrow cells or stem cells are administered through an IV, similar to a blood transfusion.

Stem cells are a versatile type of cell found in bone marrow. These cells have a unique and powerful ability: they can develop into several different types of specialized cells.

In the case of a child with SCID, the transplanted stem cells are injected into the bloodstream. They will then become healthy white blood cells that replenish immune functions — essentially building a whole new, functional immune system for the child. If the immune system regains complete function, the child may be permanently cured.

The effectiveness of a stem cell transplant for SCID depends on:

  • your child's overall health at the time of the procedure
  • the match between your child and donor's bone marrow (If the donated marrow comes from a matched sibling, the procedure has a better than 90 percent success rate.)
  • your child's age at the time of the transplant (For optimal success, a baby should have the transplant performed no later than the age of 3 months; some studies have shown that, if stem cell transplants are performed within the first 28 days of a baby's life, the success rate is as high as 95 percent.)

There can be some obstacles to a successful stem cell transplant. For instance, a suitable donor may not be available. In addition, any transplant carries a risk of a phenomenon known as graft-versus-host disease. This means that the donated bone marrow attacks the recipient, which can be a fatal complication.

What is the long-term outlook for children with SCID?

If your child's immune system is restored to good working order, he or she should be able to enjoy a rich, active adult life, including having a family.

It is important to note, some forms of SCID can run in families. For example, SCID-X1 is passed on to boys from mothers who carry the gene mutation on the X chromosome. Genetic counseling is essential for prospective parents with a family history of SCID or any other immune deficiency.