Am I able to have children if I have NDI? If so, are they likely to get it as well?
|Topic:||Pregnancy and NDI|
|Author:||Bichet, Daniel G.|
One form of inherited NDI is inherited in what is called an X-linked recessive pattern. This means that the mutated gene responsible for this form of NDI, the mutated vasopressin-2 receptor gene, is carried on the X chromosome. Females have two X chromosomes; males have one, which they inherit from their mother. So, if the mother carries a mutated X chromosome on one of her two X chromosomes, and her son inherits the mutated X chromosome, then he will express the symptoms of NDI. The reason the mother often does not express the complete symptoms of NDI is that she has another X chromosome with a healthy vasopressin-2 receptor gene that helps produce healthy vasopressin-2 receptors. This often masks the effect of the mutated vasopressin-2 receptor gene on her other X chromosome.
So, if the mother is an NDI carrier and the father does not have inherited NDI, they have a 1 in 4 chance of having an unaffected boy, a 1 in 4 chance of having a boy with NDI, a 1 in 4 chance of having an unaffected girl, and a 1 in 4 chance of having a girl who carries the mutated vasopressin-2 receptor gene on one of her X chromosomes.
The other known form of inherited NDI is caused by a mutation of the aquaporin-2 gene. This gene is carried on chromosome 12, which is an autosomal chromosome. This means that the gene is carried equally by both males and females. Normally, this form of NDI is inherited in an autosomal recessive pattern, which means that one of the two chromosome 12s carried by both the mother and the father must bear a mutated aquaporin-2 gene for their child to have a probability of being born with this form of NDI. Each of the children of the carrier mother and father stands a 1 in 4 chance of being born with NDI. And each of the children stand a 2 in 4 chance of being a NDI carrier.
X-linked NDI is rare, occurring in approximately 4 out of a million males. Autosomal recessive NDI is much more rare. And rarest of all is autosomal dominant NDI. In autosomal dominant NDI only one parent has to carry a mutated aquaporin-2 gene for their children to have a probability of being born with NDI. Each of the children of this couple stands a 1 in 2 chance of inheriting the defective aquaporin-2 gene and being born with NDI.
If your family lineage has had any sort of history of inherited NDI, you may wish to have a mutational analysis performed to see if you carry either a mutated vasopressin-2 receptor gene (females) or a mutated aquaporin-2 gene (males and females).