Severe combined immunodeficiency

Severe combined immunodeficiency (SCID) is a severe form of primary immunodeficiency, caused by a genetic mutation that affects the development and function of white blood cells, which are responsible for fighting off infections. It may result from an X-linked recessive defect in IL-2R (interleukin-2 receptor) gamma chain or an autosomal recessive defect in adenosine deaminase deficiency. As a result, individuals with SCID are highly susceptible to infections, particularly bacterial and viral infections, and often present with failure to thrive, chronic diarrhea, thrush, and recurrent infections. Treatment involves HSCT (hematopoietic stem cell transplantation, avoiding live vaccines, antimicrobial prophylaxis, and isolation to prevent catching an infection.