Regarding cystic fibrosis

Question

Hi,
I am pregnant 27 weeks and just now mother-in-law saig me that her first-born daughter passed away at 7 month old owing to cystic fibrosis.
If this disease is genetic and my mother-in-law and father-in-law are carrier hereof their son - my husband (he has twin brother) is carrier also. In my kindred no such disease, so may be that I have no this gene.
What probability that my child who have a bun in the oven will has this disease like carrier or patient?
Thank you.

Answer

Dear questioner;
the chance of your child either to be healthy, a carrier or suffering from CF is depending on certain circumstances, which we do not know at the moment and which can only be clarified if you and your husband undergo a genetic testing and counseling for CF.

However, to explain the situation a bit to you: If the sister of your husband died of CF, there is the chance of 2/3 that your healthy husband carries one CF mutation (carrier state), which he could potentially give to your child. In such a carrier state of your husband, there is the chance of 50% that he gives the CF-mutation to your child and the chance of 50% that he gives the "healthy gene" to your child. There is the chance of 1/3 that your husband has not inherited the CF-mutation from his parents, in this case he cannot give the CF-mutation to your child.

Now it is important to know, if you, as a healthy person, without CF in the family, carry a CF-mutation (even if the probability is low, it cannot be totally excluded), or if you do not carry a CF-mutation.

So 4 constellations are possible:

1. Neither you or your husband carries the CF-mutation: your child will not be suffering from CF and will not be a carrier
2. You do not carry the CF gene but your husband has a carrier state or
3. You have a carrier state but your husband has not inherited the CF-mutation: à in both cases the chance is 50% that your child is a carrier and 50% that it is not carrying the CF-mutation at all; but it will not suffer from CF.
4. Both of you are carriers of a CF-mutation: in this case the chance is 25% to get a child suffering from CF, 50% that the child is healthy but a carrier and 25% that it has not inherited one of the parent's CF mutations.

However, this explanations do not replace a genetic counseling and DNA testing for cystic fibrosis of your family (and especially of the extended family of your husband).

It is also important to understand that it may be necessary to test the parents of your husband to be able to exclude that he is a carrier. Additionally, any CFTR-mutation analysis of yourself will modify your carrier probability, but even complete sequencing of the CFTR gene will not completely rule out the possibility that you carry an undetectable mutation. However, the remaining carrier risk will usually be very low, depending on the extent of testing.

Please write me by e-mail: algirdas.utkus@santa.lt
With best wishes.
Sincerely,
Prof. Algirdas Utkus

25.01.2010