CF

Question

Our son and daughter-in-law recently had a child with CF. My family is wondering whether it would be sensible that I (grandmother) would investigate whether I’m carrier of the defective gen. They think that by doing so we can avoid further investigations in our large family.

Answer

Each individual in the population has a chance of 1/30 to be carrier of the CF-gene. However, persons who are related to a CF-patient have an increased chance of being a carrier and an increased risk of having a CF-child (risk of 1/120 instead of 1/3600).
One of the parents of your son, and one of the parents of your daughter-in-law will carry the CF-gene. The brothers and sisters of your son and daughter-in-law have a risk of 1 in 2 to be a CF-gene-carrier. A genetic test can determine who is carrier and who is not.
Relatives of the parent who is a carrier of the CF-gene again have an increased risk to be CF-carrier, which means these relatives are advised to be tested. This procedure is known as cascade-screening to identify CF-gene-carriers.
Relatives of parents who are not carriers, do not have an increased risk to be carriers themselves and do not need to be screened which means one can stop further investigations. The risk of these people to be carrier is the same (1/30) as for others in the population.
H. Cuppens

04.10.2010