Severe combined immunodeficiency

Severe combined immunodeficiencies (SCID) are inherited immune system disorders characterized by abnormalities with responses of both T cells and B cells (specific types of white blood cells needed for immune system function). Common signs and symptoms include an increased susceptibility to infections including ear infections; pneumonia or bronchitis; oral thrush; and diarrhea. Due to recurrent infections, affected children do not grow and gain weight as expected (failure to thrive). SCID may be caused by mutations in any of several genes and can be inherited in an X-linked recessive (most commonly) or autosomal recessive manner. The most effective treatment is transplantation of blood-forming stem cells from the bone marrow of a healthy person. Without treatment, affected children rarely live past the age of two.^[1]

A diagnosis of severe combined immunodeficiency (SCID) may be suspected if a baby shows any of the following persistent symptoms within the first year of life:^[2]

Eight or more ear infections
Two or more cases of pneumonia
Infections that do not resolve with antibiotic treatment for two or more months
Failure to gain weight or grow normally
Infections that require intravenous antibiotic treatment
Deep-seated infections, such as pneumonia that affects an entire lung or an abscess in the liver
Persistent thrush in the mouth or throat
A family history of immune deficiency or infant deaths due to infections

Diagnosis can be confirmed by blood tests. Blood tests show significantly lower-than-normal levels of T cells and antibodies.^[2]  

For further details on diagnosis see the following Web pages:

The Primary Immunodeficiency Resource Center provides further details regarding diagnosis of SCID. Click on the embedded link to view the page.

An article from Medscape Reference provides detailed information on the diagnosis of SCID. Click on eMedicine Journal to view the page. You may need to register to view the article, but registration is free.