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Severe Combined Immunodeficiency (SCID)

What is SCID?

SCID is a very rare disease that can be deadly. It causes a child to have a very weak immune system. As a result, the child is unable to fight off even mild infections. The disease is also known as the “boy in the bubble” syndrome because living in a normal environment can be fatal to a child who has it. This disease is passed down from parents to child (inherited).

Children with SCID become very sick with infections such as pneumonia, meningitis, and chickenpox. They can die before they reach their first birthday. But treatments are available that can be successful.

What causes SCID?

Many genetic problems can cause SCID. These problems make the white cells in the blood (T and B cells) less able to fight infection. The child's immune system has trouble defending the body against bacteria, viruses, and fungi.

There are several types of SCID. The two most common types are classical X-linked and ADA deficiency.

What are the symptoms of SCID?

Symptoms of SCID usually start within the first year of a child’s life. The following are the most common symptoms of SCID. But symptoms can occur a bit differently in each child.

Usually the child will have many serious infections, life-threatening infections, or both. The infections are not easily treated. And medicines to treat the infections do not work well. Common infections include:

  • Pneumonia
  • Repeated ear infections
  • Meningitis
  • Blood infection
  • Chronic skin infections
  • Yeast infections in the mouth and diaper area
  • Diarrhea
  • Liver infection (hepatitis)

How is SCID diagnosed?

The healthcare provider will ask about your child’s symptoms and health history. He or she will give your child a physical exam. Your child may need multiple blood tests to help confirm the diagnosis.

How is SCID treated?

Treatment will depend on your child’s symptoms, age, and general health. It will also depend on how severe the condition is.

Treatment for SCID includes:

  • Treating the current infection
  • Avoiding germs and preventing exposure to new infections
  • Fixing the immune system problem (immunodeficiency)

The best treatment for this disease is a bone marrow transplant, which offers a chance of a cure. In a bone marrow transplant, bone marrow cells are transplanted from a healthy person to the child. Bone marrow is the soft, spongy tissue found inside the bones. It helps blood cells form, and is the place where the body stores blood cells.

A bone marrow transplant has the best chance of working if it is done during a child’s first 3 months of life. The goal of bone marrow transplant is to help the child’s immune system work better. Cord blood may also be used for the transplant.

Researchers have had some success using gene therapy to treat SCID. But gene therapy is still in the experimental stages.

Can SCID be prevented?

Since this disorder is inherited, parents of children with SCID should think about talking with a genetic counselor. The counselor can discuss genetic testing and family planning with them.

Key points about SCID

  • SCID is a disease that passed on from parents to children (inherited).
  • It is a very rare, life-threatening disease.
  • The disease causes a child to have very weak immune system.
  • The best treatment for this disease is a bone marrow transplant.
  • Parents of children with SCID should talk with a genetic counselor about genetic testing and family planning.           

Next steps

Tips to help you get the most from a visit to your child’s healthcare provider:
  • Before your visit, write down questions you want answered.
  • At the visit, write down the names of new medicines, treatments, or tests, and any new instructions your provider gives you for your child.
  • If your child has a follow-up appointment, write down the date, time, and purpose for that visit.
  • Know how you can contact your child’s provider after office hours. This is important if your child becomes ill and you have questions or need advice.