A Family Guide to Non-Oncologic Blood Disorders
Severe Combined Immunodeficiency
What is severe combined immunodeficiency? Severe combined immunodeficiency (SCID) is a group of inherited disorders that results from a defect in the immune system. SCID is called “combined” immunodeficiency because it affects the function of two kinds of infection-fighting cells. As a result, there are reduced or broken T- and B-lymphocytes (specialized white blood cells made in the bone marrow and the thymus gland to fight infection). When the immune system does not work properly, the child’s body is unable to fight off infections. SCID often is known as the “boy in the bubble” syndrome. There are 14 forms of SCID. The most common form is caused by a problem in a gene found on the X chromosome and affects only males. Females may be carriers of this condition. Another form of SCID is caused by a deficiency of an enzyme (a protein) that is needed for lymphocytes to develop. What are some symptoms of SCID? Symptoms of SCID typically develop within the first few months of life. The following are the most common symptoms of SCID. However, each child may experience symptoms differ- ently. Symptoms may include: • Frequent ear infections and sinus infections that do not respond to antibiotics • Developing an infec-
What tests and procedures will my child need? • Blood work: » » Complete blood count (CBC)—shows the de- creased number of lymphocytes (white blood cells that help fight infection) » » Immunoglobulins—levels of antibodies in the blood (IgA, IgE, and IgM) will be low » » T-cell mitogen response—tests the response of T cells to a chemical substance. A typical response is absent or low (this means that the child is unable to fight off an infection because the T-cells response is not working). • Chest X-ray may or may not be performed. The purpose is to view the thymus gland. The thymus is an organ that is located in the upper chest behind the breast- bone where immune cells called T-lymphocytes mature and multiply in early life. How is SCID treated? Stem cell transplant (SCT) is the only curative option. Below are treatment options to help alleviate the symptoms of SCID: • Immediate referral to a pediatric immunologist (a doctor who specializes in abnormalities of the immune system) • Basic precautions » » Avoid large crowds, dirty environments, and sick people » » Strict handwashing » » Use medications to treat any active infections. In some cases, if the infection is severe, your child may need to be hospitalized to receive these med- ications intravenously (i.e., IV): −− Antibiotics treats bacterial infections −− Antifungal treat fungal infections −− Antiviral treat certain viral infections » » Avoid live vaccines (rotavirus, varicella, measles, mumps, rubella [MMR]) • Intravenous Immune Globulin (IVIG) is a blood product given intravenously that provides temporary antibodies to try and protect your child from getting some of the infections that they are susceptible to.
• Pneumonia (infection in the lungs) • Meningitis (infection of the spinal cord) • Sepsis (infection of the blood stream) • Chronic skin infections • Yeast infections in the mouth and diaper area • Diarrhea
tion after receiving a live vaccine (e.g., rotavirus)
• Poor growth and development
How is SCID diagnosed? A diagnosis of SCID is usually made during the first year of life based on the following: • Complete medical history and family history • Physical examination • Specific blood tests and possible X-ray • Newborn screening (currently available in 12 states and Puerto Rico)
Severe Combined Immunodeficiency
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