Combined immunodeficiency, or “severe combined immunodeficiency” (SCID), is a group of rare disorders, and is caused by a genetic mutation.
Newborns with SCID are very susceptible to severe infections, though they appear healthy at birth. SCID is fatal within the first two years of life unless immunity-restoring treatments — such as stem cell transplants, gene therapy, or enzyme therapy — are given.
To recognize infants with this disorder, a healthcare provider takes a few drops of blood from the baby's heel. The blood sample is sent to a laboratory to test for several such severe disorders.