What Causes Severe Combined Immunodeficiency (SCID)?

Severe combined immunodeficiency (SCID) is a life-threatening condition characterized by the inability of the immune system to produce functional T and B cells, making it difficult for the body to fight off infections. The disease was first reported in 1950 by Glanzmann and Riniker, and since then, significant progress has been made in understanding its molecular basis.

Previous classification systems for SCID were based on the presence of molecular defects affecting T cell numbers and the presence or absence of defects affecting B and/or NK cell numbers. However, with advances in molecular biology and the Human Genome Project, a more accurate classification system was developed based on particular molecular defects detected.

One of the most common genetic conditions responsible for SCID is a mutation of the common γ chain of the interleukin (IL) receptors, accounting for approximately 50% of all patients with SCID. Adenosine deaminase (ADA) deficiency is another significant mutation that accounts for about 20% of all SCID cases.

The discovery of the molecular basis of X-linked human SCID in 1993 was a major breakthrough in understanding the disease. This led to the development of newborn screening tests, which have significantly improved outcomes for patients with SCID. Early diagnosis and treatment through hematopoietic cell transplantation (HCT) can result in survival rates as high as 95% among patients transplanted under 3.5 months of age without infection.

Symptoms of SCID typically appear in the first year of life and may include recurrent severe infections, chronic diarrhea, and failure to thrive (FTT). Without timely diagnosis and treatment, SCID can be a life-threatening condition, with affected individuals often dying from overwhelming infections before their first or second birthdays.

In conclusion, SCID is a complex disease caused by various molecular defects in the development and function of T and B cells. Understanding its causes is crucial for developing effective treatments and improving outcomes for patients with this devastating condition.

What causes scids