X-linked disorders are so named because they are caused by genes located on the X chromosome. Females have two copies of the X chromosome, while males have one X and one Y chromosome. The single copy of the X chromosome puts males at an increased risk of having X-linked disorders. Assessing just the mother’s carrier status is enough to determine the risk of having an affected child. A carrier mother has a 50% chance of passing on her mutated copy of the gene to her children. Carrier females typically exhibit mild symptoms or none at all because they still possess one healthy copy on their other X chromosome. However, all sons who inherit the mutated gene will be affected with the disease because they have no healthy copies to compensate.
Since screening the mother’s genetic background is sufficient to evaluate the risk of X-linked disease, patients using egg donors should consider screening for these disorders as disease-causing mutations may originate from the donor. Our Comprehensive panel tests for 124 X-linked diseases. For a full list of disorders included on this panel, click here.