Buffy it depends on the genetic mutation, in many cases, as to how the disease presents and how long a person can go undiagnosed. Clearly this lady did not have profound digestive or respiratory problems for the early decades of her life (and therefore probably has a 'less life threatening' form of CF).
Over 80% of cases of CF are caused by the Delta F 508 gene. My son carries two copies of this. Subsequently he has the potential to have serious lung and digestive system issues. Someone with one DF508 gene and one other type of CF gene may present differently although not necessarily more mildly.
Genes do not tell the whole story though.. lifestyle has a lot do with it, as do many other factors.
When my son was about 5, 'cascade screening' via a simple mouth wash test was offered to the relevant members of mine and ex H's entire family. Ex H has 3 siblings.. he is obviously a carrier (as am I.. having only 1 gene does not cause CF).. one other was also a carrier, one was entirely clear of CF genes and to our shock, one brother was diagnosed with a CF.. a 'different kind' of CF to DS's.. he carried one DF508 and one of the other identified genes (of which there are currently 12 in total) and therefore had a type of CF that had mangaged to diguise itself for almost 30 years. Poignantly, the only 'effects' of his CF that he has ever suffered to date is the infertility aspect (97% of male CF sufferers are infertile) and so far, he and his wife have been unsuccessful in trying to have a baby even with intervention.
DS knows he is almost certainly unable to be a father at least without a lot of 'help'. I told him at a very young age, when he first learned how babies were made, and when he was too young to 'care' so that he would grow up with the knowledge and gradual and not have any nasty shocks.
Similarly, he has gained a gradual knowledge of the life threatening aspect. He has known for a few years that the average official life expectancy still stands at 31 years (this dawned on him when Alice Martineau, a talennted young singer whose career we were following and who died shortly after releasing her first album) died at the age of 30. He asked the question I had always dreaded "Mum.. Alice was only 30.. is that when I'm going to die?" I handled it, as I had planned to, by pointing out that he has managed to stay very well and that he lives in a time of great technological advance and the prospect of gene therapy, and so the official statistics need not necessarily apply to him. (And then, obviously, in private, I balled my eyes out! )
I am really proud of him. He is a fit, clever, gorgeous -looking ((I man be biased! ) well balanced young man in general and he recently got an award at school (on school presentation night) for 'exceptional strength and character'. He and I are very similar and fall out quite a lot.. but I reassure myself that I must be be doing something right.
And the 'good health' thus far I put down to the swimming. DS trains for 4 hours a week.
If I could give Gordon and Sarah one bit of advice I would say "Enrol Fraser in a swimming club.. NOW.. so he can start when he is 4 or 5 years old like DS did." Fortunately, we don't fall out over swim training. He can FEEL how good it is for his lungs.. and he likes the shoulder muscles and the six pack he is developing!