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combination of DF508/R750Q

Question
I am 21 weeks pregnant in my first child and I was found to carry the DF508 mutation in heterozygote status. My husband was found to carry the R750Q mutation, also in heterozygote status. I would like to ask:
1. What are the chances of the fetus inheriting both genes?
2. What mild symptoms does this combination result in?
3. Is there a chance of the symptoms being severe?
4. What is the chance of sterility?
Answer
Dear friend,
You are pregnant at 21st week and you were tested for CF mutations. You were found to carry the R750Q mutation and your husband the DF508 mutation, both in heterozygote state. The chances for your fetus are 50% to be a heterozygote like you, carrying the R750Q mutation, or the DF508 mutation, 25% to carry no mutation at all and 25% to be a homozytoge, carrying both R750Q and DF508.
In order to assess the clinical significance of the CF mutations, as it will be expressed in the dysfunction of the CFTR protein, a large international database (CFTR2) has been established. During the last registry (8/12/2017), based on data from 89059 CF patients, the following record exists:

312 mutations cause CF
36 mutations have variable clinical manifestations
13 mutations do not cause CF
13 mutations are of unknown clinical significance.

Based on the latest registry the combination of R750Q/DF508 does not cause typical severe CF.
There may be the chance, if it is a boy, to present bilateral congenital absence of the vas deferens (Ranvik-Glavac M, 2000), or pancreatitis (Jessica LaRusch 2014).

Yours friendly,
Dr. Stavros Doudounakis
25.05.2018