What does the following term mean: Heterozygous carrier of the Delta-F-508 mutation?

Question

Hello,
today I got the result from the children's hospital per mail for my 16-year-old son, i.a. a molecular genetic investigation has been done.
The result is the following: "Heterozygous carrier of the Delta-F-508 mutation in exon 10 of the CFTR-gene." As those medical terms do not mean anything to me, I typed the term in "google" and understood, that it seemingly deals with CF.
I want to ask you for explanation of the medical term, especially if it allows a conclusion on the course / severity of the disease and if yes, which one.
The doctor at the hospital only explained at that time to me, that he wants to check with the molecular genetic investigation, if there is probably a "mini-CF" underlying, that however only hardly shows symptoms and either does not need any therapy. Is there anything like a "mini-CF" at all and does the above mentioned result mean that my son suffers from CF?
Many thanks!

Answer

Dear questioner,
all humans have inherited two copies of the CFTR gene (one from the father, one from the mother), that is important for CF. The genetic variant "Delta-F-508 mutation in exon 10 of the CFTR-gene" is an illness-causing mutation, however only if BOTH copies of the gene are inoperative. I conclude from the term "carrier" that only one CF-mutation has been found in your son - thereby he is as healthy as the parent he has inherited this copy from (as also this parent is a heterozygous carrier of the mutation F508del). In case there is no more information on the genetic result, the followinf applies: your son does not suffer from CF, the illness is autosomal-recessive and only occurs in case the patient has two CF-mutations.
Now to the "mini-CF": there are illnesses, where a carriership for CF is found more frequently (also like in your family: a healthy and an inoperative CFTR-gene). The most popular are distrubances of fertility, however I conclude from the age, that your son is not under medical treatment for this. Furthermore, there are illnesses of the airways that are also seen more frequently in patients with a carriership for CF. I assume that the doctor in the hospital meant such a so-called CFTR-related disease and therefore did a CFTR-mutation analysis.
Yours sincerely,
Dr. Frauke Stanke

08.07.2013