The small sacks in the lungs called alveoli are very thin , much thinner than a hair , in some cases damage can occur to those alveoli.
Then a little hole falls into it and your lung deflate
This causes quite some pain and shortness of breath , as I had it happen myself it feels like a BAD muscle pain that doesn't resolve quick.
You get quite a strange dry hacking cough , if this ever happens to you call a doctor or your cf clinic and let them listen to your lungs and get a thorax (lung) x-ray.
The distal intestinal obstruction syndrome or when the plumbing gets clogged.
Sometimes the thick mucus present in your intestines together with food can cause a very mean and nasty blockage.
This is extreme painful and it gets worse after eating.
If this happens and you didn't forget your enzymes , call a doctor , this situation could be quite dangerous.
About 20% of CFers develop nasal polyps (growth of extra tissue in the nares).
Allergies, infection, and polluted air situations can cause the polyps.
When you have nasal polyps its difficult to breath through your nose and you could lose the ability to smell hamburgers when you are walking along mcdonalds.
With many CFers, asthma is another complication , which often means more medicines and more risks for infections. It would be wise with CF and asthma to test for allergies as allergies are often the first cause of asthma.