X-linked lymphoproliferative disease (XLP) is a disorder of the immune system and blood-forming cells that is found almost exclusively in males. More than half of individuals with this disorder experience an exaggerated immune response to the Epstein-Barr virus (EBV). EBV is a very common virus that eventually infects most humans. In some people it causes infectious mononucleosis (commonly known as "mono"). Normally, after initial infection, EBV remains in certain immune system cells (lymphocytes) called B cells. However, the virus is generally inactive (latent) because it is controlled by other lymphocytes called T cells that specifically target EBV-infected B cells.

Mutations in the SH2D1A and XIAP genes cause XLP. SH2D1A gene mutations cause XLP1, and XIAP gene mutations cause XLP2.

XLP1 is estimated to occur in about 1 per million males worldwide. XLP2 is less common, occurring in about 1 per 5 million males.

This condition is generally inherited in an X-linked recessive pattern. The genes associated with this condition are located on the X chromosome, which is one of the two sex chromosomes. In males (who have only one X chromosome), one altered copy of an associated gene in each cell is sufficient to cause the condition. A characteristic of X-linked inheritance is that fathers cannot pass X-linked traits to their sons.

Published Date: May 17, 2021Published By: National Institutes of Health