Which clinical history findings are characteristic of X-linked severe combined immunodeficiency (XSCID)?

Updated: Aug 11, 2020
  • Author: Francisco J Hernandez-Ilizaliturri, MD; Chief Editor: Emmanuel C Besa, MD  more...
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X-linked severe combined immunodeficiency (XSCID) is by far the most common form of SCID, accounting for almost 50% of cases. [16]  As the affected gene is located in the X chromosome (X13q band), the disease is limited to males. Because of a defective common gamma chain (a component of cytokine receptors for interleukin-2 [IL-2], IL-4, IL-7, IL-9, and IL-15), signal transduction cannot proceed normally, which results in SCID characterized by absent T and NK cells and dysfunctional B cells. The phenotype is T–B+NK–.

Infections begin in the first months of life, affecting the upper and lower respiratory tracts, gastrointestinal tract, and skin, whereas X-linked agammaglobulinemia (XLA) does not manifest clinically until the second half of an infant's first year of life. Persistent opportunistic infections with Candida albicans or P jirovecii and viral infections with varicella-zoster virus, CMV, and Epstein-Barr virus are common. The risk of GVHD is high in these patients because of their inability to reject foreign antigens

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