Hi I Have Hi I Have Pulmonary Fibrosis And Emphysema

Hi i have hi I have pulmonary Fibrosis and Emphysema I have had it for about four years but have only seen the Dr for the past year. With test and cat scans. My question is where does the scare tissue come from. I was offered the new drug Estriet but refused it because of the side effects. Yes I am so n oxygen level 3/4 at times. The dr snd I have talked about the end snd I am now taking three months of summer to relax and digest every thing. But where does the scare tissue come from? Thank you for your help.