Severe Combined Immunodeficiency (SCID)

What is SCID?

SCID is a group of very rare, life-threatening diseases that are present at birth. The disease causes the child to have very little or no immune system. As a result, the child's body is unable to fight off infections. This disease process is also known as the "boy in the bubble" syndrome because living in the normal environment can prove fatal to these children.

Children with this rare, inherited disease become very ill with illnesses such as pneumonia, meningitis, and chickenpox and can die within the first year of their life. With new advances in treatments, however, children with SCID can be successfully treated.

What causes SCID?

SCID is a group of inherited disorders. Many genetic defects can cause SCID. These defects reduce the ability of white cells in the blood to fight infection.

There are several types of SCID, but two most common types are the classical X-linked (inherited on the X chromosome and only affects males) and the ADA deficiency (low levels of the enzyme ADA resulting in a decline of T cells and B cells).

What are the symptoms of SCID?

Symptoms of SCID usually become apparent within the first year. The following are the most common symptoms of SCID; however, each child may experience symptoms differently. Symptoms may include:

  • Numerous, serious, and/or life-threatening infections that are not easily treated and do not respond to medications (as they would in children without SCID), including the following:

    • Pneumonia. An infection of the lungs.

    • Meningitis. An infection of the brain.

    • Sepsis. An infection in the bloodstream.

  • Other infections, including the following:

    • Chronic skin infections

    • Yeast infections in the mouth and diaper area

    • Diarrhea

    • Infection of the liver

How is SCID diagnosed?

A diagnosis of SCID is usually made based on a complete medical history, family history, and physical examination of your child. In addition, multiple blood tests may be ordered to help confirm the diagnosis.

Treatment for SCID

Specific treatment for SCID will be to:

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  • Treat the current infection

  • Avoid germs and prevent exposure to new infections

  • Correct the immunodeficiency

What is bone marrow transplant?

The best treatment for this disease is a bone marrow transplant (BMT), which, in most cases, would cure the problem. A bone marrow transplant involves taking cells that are normally found in the bone marrow (the soft, spongy tissue found inside the bones that is responsible for the development and storage of blood cells), and giving them back either to the patient or to another person. The goal of bone marrow transplantation is to infuse healthy bone marrow cells into a person after their own unhealthy bone marrow has been eliminated. BMT would help increase the sick child's immune system.

What are other treatment options?

Other treatment options include enzyme therapy and intravenous immune globulin or gamma globulin treatments, also called IVIG. These treatments involve giving the child injections to help boost his or her immune system, and treating each infection very promptly and accurately. In addition, researchers have had some success using gene therapy to treat SCID. However, gene therapy is still in the experimental stages.

Since this disorder is genetic, parents of children with SCID should consider talking with a genetic counselor about genetic testing and future family planning.