TRECS are formed during normal immune system development as T-cell lymphocytes within the thymus gland undergo differentiation and specialization following exposure to antigens. In Illinois, newborn screening for SCID is performed by measuring the T-cell receptor excision circles (TRECS) in DNA extracted from dried blood spot samples. Newborn Screening and Definitive Diagnosis Infants with SCID also may suffer from poor nutrition and “failure to thrive.” Without early diagnosis and treatment, children with SCID usually succumb to infectious disease complications during the first or second year of life. Often these infections are prolonged and do not respond to usual therapies, and some may require intravenous antibiotics. Early symptoms may include frequent bouts of ear infections, thrush, bronchitis, pneumonia and diarrhea. Lacking adequate immune system defenses, these infants are very susceptible to multiple life threatening infections.

Newborns with SCID usually appear healthy at birth and may have no family history of immunodeficiencies.

All forms of SCID are inherited and not acquired as side-effects of infection or immune response suppression therapies. Individuals with SCID are very susceptible to recurrent infections and without treatment may succumb to pneumonia, meningitis or other infection related complications. These lymphocytes serve as primary defenses in the identification of invading viruses, bacteria and fungi and help facilitate the immune system’s response to pathogenic invasion. Severe combined immune deficiency (SCID) includes a group of rare inherited disorders in which genetic defects cause improper development of special white blood cells, the T lymphocytes. Severe Combined Immune Deficiency Information for Physicians and Other Health Care Professionals Definition

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