My husband's grandmother had three children. Two of her sons with Wiskott Aldrich syndrome (WAS) died at ages 7 and 3. My husband's father did not have it, and he had 3 boys. My husband and I are expecting. Is there a chance our child will have WAS?
Wiskott Aldrich syndrome (WAS) is inherited in an X-linked recessive manner. A condition is X-linked if the responsible gene is located on the X chromosome. The X chromosome is one of the two sex chromosomes (the other sex chromosome is the Y chromosome). Females have two X chromosomes in each cell and males have an X chromosome and a Y chromosome in each cell.
Although females have two X chromosomes, one of the X chromosomes in each cell is "turned off" and all of the genes on that chromosome are inactivated. Females who have a mutation in a gene on one of their X chromosomes are called carriers of the related condition. Carrier females usually do not have symptoms of the condition because usually the X chromosome with the mutated gene is turned off. Therefore, they have another X chromosome with a working copy of the gene. Sometimes, the X chromosome with the working copy of the gene is turned off, which may cause symptoms of the condition. However, females with symptoms are usually much more mildly affected than males. A male has only one X chromosome, so if he inherits a mutation on the X chromosome, he will have signs and symptoms (be affected).
Males with an X-linked recessive condition always pass the mutated gene to all of their daughters, who will be carriers. A male cannot pass an X-linked gene to his sons because males always pass their Y chromosome to male offspring.
Female carriers of an X-linked recessive condition have a 25% chance with each pregnancy to have a carrier daughter like themselves, a 25% chance to have a non-carrier daughter, a 25% chance to have an affected son, and a 25% chance to have an unaffected son. This also means that each daughter of a carrier mother has a 50% chance of being a carrier, and each son has a 50% chance of having the condition.
Last updated: 4/10/2015
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