Rituxan can cause severe breathing problems, something to do with an enzymatic reaction in the lungs. It's been 3 years since I went off for that reason, and I am just starting to be able to breath normally.
Then there is Rheumatoid Lung Disease. A simple X-ray will show RA nodules in the lungs. Not sure how they treat it, I haven't had it yet.
Another thing is methotrexate lung. That is definitely cause by mthx. I never had that, although I was on mthx for 9 years. Instead, I had liver problems and had to go off, although it worked 100% in combo for me on Kineret. Those were the days!
"More than that, we rejoice in our suffering, knowing that suffering produces endurance, endurance produces character and character produces hope. And hope does not disappoint, because God's love has been poured out through the Holy Spirit who has been given to us." Romans 5:3-5