Combination of mutations and impact on the child

Question

My husband carries the DF508 mutation and the normal genotype 9T/9T/. I carry in heterozygote status the allele TG11 - 5T at intron 8 of the CFTR gene as well as the normal genotype 5T/7T/. My son carries the allele TG11 - 5T at intron 8 and is characterized as a carrier of a mild CF mutation. What problems can this cause and what should we do now that I am 4 months pregnant?

Answer

Dear friend,
Your husband is a carrier of the DF508 mutation and you carry the allele TG11 - 5T at intron 8 of the CFTR gene.
Your first child is a carrier of a very mild CF mutation, the TG11 - 5T, just like you (Castellani 2008).
The embryo you carry has a 75% probability to be normal. There is a 25% probability that the embryo will carry the combination of the DF508 and TG11 - 5T mutations. If it is a girl there will be no symptoms. If it is a boy it will have increased chances to present congenital bilateral absence of the vas deferens (CBAVD) (Moscowitz 2008), according to the paper from Castellani et al 2008, TG11-T5 is highly unlikely to cause disease. Please notify also, that the individual clinical course cannot be predicted according to the genotype, as many other genetic (modifier genes, etc.) and environmental factors play a role and the severity of disease differs substantially even between patients with the exact same mutations.
Yours friendly,
Dr. Stavros Doudounakis

17.12.2013