I was diagnosed with this at the age of 50.It 's a funny thing and in some people it burns itself out after a while and in others it turns in on itself and gets worse.It's an autoimmune disease.It can be controlled by drugs .As the previous posters have said it affects different people different ways.Mine more or less burnt itself out after a couple of years but left me with severe osteoarthritis.
It is horrible..you are tired and feel as if your whole body is on fire ..it attacks the joints (in my case the hips) and you just feel like cr*p.
I do sympathise with your friend and anyone else who has to suffer with this.
My mantra is ..keep moving .
Try and ride through the pain.
Look at your diet .
Drink plenty of water.
It does affect your life.
One day you feel OK and the next you feel awful and just want to lay about in bed.
I find the weather affects it. I dread the cold and damp.
Have a look here
http://www.arc.org.uk/default.htm