Severe combined immunodeficiency (SCID)

What is SCID?

Severe combined immunodeficiency (SCID) is one of the most severe types of primary immunodeficiency (PI). Babies born with SCID lack white blood cells called T cells. T cells not only directly attack cells infected with viruses, bacteria, or other microorganisms, but they also cause B cells, another type of white blood cell, to produce antibodies.

How is SCID diagnosed?

Babies born with SCID appear healthy at birth but are unable to fight infections. The newborn screening blood test can show if a baby has a low number of T cells, a sign that a baby may have SCID. A lack of T cells is essential to SCID diagnosis, but no or low T cells may also occur in other health conditions.It takes time to perform a thorough evaluation of a baby found to have no or low T cells.

What’s the best way to protect a baby with suspected or confirmed SCID?

If a child’s newborn screening blood test shows low T cells, try to stay calm and remember that you are not alone. The clinical immunologist can help you every step of the way during this sometimes confusing and challenging process.

What causes SCID?

Variants in at least 20 different genes can cause SCID. Although the types of SCID vary with respect to the cause of the immunodeficiency, their laboratory findings, and their pattern of inheritance, infants with any type of typical SCID have severe deficiencies in both T cell and B cell function.

What are the clinical signs and symptoms of SCID?

Infants with SCID have no outward appearance to distinguish them from normal newborns and are usually clinically well until they have an infection. For those not detected by newborn screening, an excessive number of infections is the most common presenting symptom of infants with typical SCID. These infections are not usually the same sorts of mild infections that children without PI have, such as frequent colds.