i was diagnosed at 16 although I showed symptoms my whole life and did indeed almost die before getting diagnosed.
I also had multiple other issues as a small child...which a) kept my doctors and parents busy b) had some of the same symptoms as CF.
For instance I had awful food allergies...dairy products, eggs, pecans etc. So I couldn't eat a whole lot...I lived on lean meat and vegetables..no fast food or really fatty food because most of that stuff had allergens in it. Therefore I was skinny and also because of my diet didn't show a lot of symptoms of malabsorption though I did show some.
Because of my history of food allergies when I started having sinus and lung issues it was blamed on enviromental allergies and asthma...even when allergy tests came back negative.
It wasn't until all treatments had been exhausted and I was still sick...deathly ill at that point that more indepth testing was done...CF, immune system work up, A1AT etc etc.
CF is good at masquerading! And its symptoms are pretty common and easily diagnosed as other things.
When you hear hoof beats think horse not zebras! is what I hear a lot of doctors say and CF is a zebra!