Ah, something I can relate to.
I was diagnosed with this a few years ago, and believe me it's not pleasant.
Lost 10kg and spent a few days in hospital on a drip. Requires daily medication which lowers your immune system.
It's not just the unpleasant stuff, there's other horrible conditions, such as arthritic-like pains, constant tiredness and having to really watch your diet.
However, it can be managed once the right medication is found, and I'm playing sport at a decent level in spite of it. Wish him all the best and can definately understand the break he is taking, as he will need it.