I Have A Friend Who Has Lost 50 Pounds Fast

I have a friend who has lost 50 pounds fast and unexpectedly. Also both of his ankles and feet are severely swollen. Has been continuously swollen for months. The foot area is discolored (very dark red) and very difficult to walk. He is 6'5. weighs 170, is 67 yrs old and I am sure has copd.
Is there some article or paper that can shed some light on possible causes.