Aicardi syndrome most often appears in females as well as in boys with Klinefelter’s syndrome, a condition in which a male has an extra X chromosome. For these reasons, researchers believe the disorder is caused by a defect on the X chromosome.
People normally have 46 chromosomes in each cell. Two of the 46 chromosomes are sex chromosomes, known as X and Y. They help determine whether someone will develop male or female sex characteristics. Females have two X chromosomes, while males usually have one X chromosome and one Y chromosome.
During the normal development of an embryo, there should only be one active X chromosome in each cell. This means that one of the two X chromosomes in a female embryo must randomly deactivate during cell formation. In the case of Aicardi syndrome, researchers think that the deactivation of the X chromosomes fails to alternate randomly. As a result, one X chromosome is active in more than half of the body’s cell formations. This is called “skewed X-inactivation.”
Researchers have yet to determine the exact gene that causes skewed X-inactivation, so the cause of the disorder is still not known. This lack of information also makes it difficult to determine the risk factors for Aicardi syndrome.