Article: X-linked severe combined immunodeficiency

What is X-linked severe combined immunodeficiency?

X-linked severe combined immunodeficiency (SCID) is an inherited disorder of the immune system that occurs almost exclusively in males. Boys with X-linked SCID are prone to recurrent and persistent infections, including infections with organisms that ordinarily do not cause illness in healthy people. Some of these infections can be very serious or life-threatening in boys with X-linked SCID. Many infants with the condition also experience chronic diarrhea and skin rashes, and may grow more slowly than other children. Without treatment, affected males usually live only into infancy.

How common is X-linked severe combined immunodeficiency?

X-linked SCID is the most common form of severe combined immunodeficiency. The exact incidence is unknown, but the condition probably affects at least 1 in 50,000 to 100,000 live births.

What genes are related to X-linked severe combined immunodeficiency?

Mutations in the IL2RG gene cause X-linked severe combined immunodeficiency.

The IL2RG gene makes a protein that is essential to immune system function. The protein plays a role in the maturation of immune system cells called lymphocytes, which defend the body against potentially harmful invaders (such as viruses), make antibodies, and help regulate the entire immune system. Mutations in the IL2RG gene prevent these cells from developing and functioning normally. Without functional lymphocytes, the body is unable to fight off infections.

How do people inherit X-linked severe combined immunodeficiency?

This condition is inherited in an X-linked recessive pattern. A condition is considered X-linked if the gene that causes the disorder is located on the X chromosome (one of the two sex chromosomes). In males, who have only one X chromosome, one altered copy of the gene is sufficient to cause the condition. In females, who have two X chromosomes, a mutation must be present in both copies of the gene to cause the disorder. Males are affected by X-linked recessive disorders much more frequently than females.