Severe Combined Immunodeficiency (SCID) | Symptoms and Causes

What are the symptoms of severe combined immunodeficiency?

Severe combined immunodeficiency (SCID) can be difficult to detect because babies with the disorder may not show any signs of illness until they develop a telltale infection. In most cases, infections are the first indication that a child may have SCID, though in some children the first sign is a failure to thrive.

What causes SCID?

There are more than 15 recognized kinds of SCID, but the most common type, known as SCID-X1 (for “X-linked severe combined immunodeficiency”), involves a defect in a gene on the X chromosome. Because girls have two X chromosomes while boys have only one, SCID-X1 affects only male children. However, girls can be “carriers” and can pass the disorder on to their own sons later in life.

Different genetic defects cause each form of SCID. But all types of SCID are genetic — meaning they are caused by an error or mutation in the child’s genes.

Even though SCID is a genetic condition, having one child with SCID does not necessarily mean other family members, including siblings, are going to develop the disease. However, it is a good idea to ask your doctor about genetic counseling for you and your other children.