Hi Amanda,
Yes, you need to have a mutation on both CFTR genes in order to have CF (barring exceedingly rare genetic anomalies.) However, in a certain small percentage of those with CF, both genes cannot be identified, because even genetic sequencing does not analyze 100% of the gene and no technology is perfect. In the case of my daughter, she has one copy of the df508 mutation (the most common- only a small percentage of the cf population does not have at least one copy of this one) but we don't know her other one. We just know she HAS the disease vs. just being a carrier due to her symptoms, the sweat test (108) and her response to treatment. If your kids have not had genetic sequencing done yet- they need it. A panel test is not enough, as it only looks for something like 30ish-100ish mutations. You want Ambry Amplified for CF w/deletions and duplications, if at all possible. Now, if you've had it, and are still stuck with no clear answers- I'm so sorry- but you do need that as a starting point.
Re your carrier etc questions:
Generally speaking, yes, when someone presents with one mutation of a autosomal recessive disease, they would be considered a carrier, and usually carriers cannot be symptomatic for one of those diseases, since the 'good' gene would be the dominant one. However, things are *not* proving to be so black and white with CF. It's possible- for some reason- for some carriers to be symptomatic. I believe this is due to there being other factors that impact the CF gene and exacerbate it's effects on the body; a lot of research is being done in this area. But yes, symptomatic carriers can have similar issues... not to the level of severity as someone who has the disease though. If someone was experiencing progressive disease and had been considered a carrier only, I'd certainly hope the dr would consider the possibility that an unknown 2nd mutation was present and the person actually had cf!