Mild, moderate or severe is merely a label used to assess current lung function. It doesn't imply lifespan nor even progression fo the disease. In this day and age, with the advancements that have been made in treating CF and the proactive and aggressive treatment regiments being utilized, the hope is that ALL young children with CF are classified as mild irt their lung functions.
However, all that means is where your child's lungs are today. CF is progressive. You aren't born with all the lung issues, they happen over time. And, over time, all typical CFers progress from mild to moderate and ultimately to severe. Atypical CFers is a totally different matter. You cannot predict at what pace a typical CFer will progress, but eventually they will progress.
The reason people put so much stock in this classification is because normally it is your lung function which determines your life expectancy with CF. Normally, it is your lungs that fail and you ultimately die from that failure.
That is not always the case at all. And, someone with a mild presentation of lung involvement can have far, far worse involvement in other areas.
IRT lung function, our ds is classified as mild. Considering it isn't his lungs which will kill him, the classification means very little to me at this point. We have "a few years" left with our son. He already has a palliative care plan in place with his Heptalogist. It is genuinely my hope that his lung involvement remains mild to the end for him. I think it would be horrifically cruel for him to have to face what is already in his future while struggling to put air into his lungs as well. But, simply put the classification of mild, moderate versus severe is merely a medical term to clarify where the lungs are currently. I suspect most CF doctors hestitate to use it with families because it doesn't even begin to convey the reality of CF, it merely denotes where the lungs are currently.