Severe Combined Immunodeficiency (SCID)

Symptoms of severe combined immunodeficiency (SCID)

For infants with SCID that isn’t detected by newborn screening, an excessive number of infections are the most common symptom. These may include more serious infections like pneumonia, meningitis, or bloodstream infections. Infants with SCID are also more susceptible to pneumonia caused by a dangerous organism called Pneumocystis jirovecii that must be diagnosed and treated quickly.

Some organisms that cause mild or moderate discomfort in healthy children, like chicken pox (varicella), or vaccines, may be very dangerous to children with SCID. Fungal (yeast) infections may be very difficult to treat in a child with SCID. For instance, yeast infections of the mouth (thrush) or chronic skin infections may occur in babies with SCID.

Persistent diarrhea that results in failure to grow or malnutrition is also common among children with SCID.

Diagnosis of severe combined immunodeficiency (SCID)

Early diagnosis is important so SCID can be addressed before an infant has had a chance to develop infections that could lead to later complications.

Thanks to the tireless work of doctors and parents who had lost children to SCID, the Department of Health and Human Services (HHS) announced in 2010 the addition of SCID to the recommended uniform screening panel. Now, all 50 states are screening for SCID.

As the technology emerges, more newborn screening tests will be available for different types of PI. Now, nearly every infant with SCID in the US can be diagnosed within days of birth. If the mutation responsible for a sibling’s SCID is known, a genetic test can be conducted in utero to diagnose an unborn child.

Two blood tests are used to reach a diagnosis. The first is a complete blood count, and the second is a count of each type of white blood cell (lymphocyte), including both T cells and B cells. If the lymphocyte count is low, additional tests are conducted to count T cells and measure their function to confirm the diagnosis.