Rectal abscess in a "normal" person?

So my brother has had a rectal abscess this week. It drained on it's own today. Got very large, and right next to his anus. Here is the thing. He is 32 years old, but very disabled. He is a very low functioning autistic man. He can not speak, clean after himself, dress himself ect... My Mom is his care giver. So naturally when she found this yesterday it scared her, because of me.

He's also had some minor amounts of bleeding. But honestly from what she's told me it's nothing more then maybe what a hard bowel movement would cause. It wasn't often either, so it wasn't something I thought was a concern.

But being a Crohn's patient myself, that has had a abscess and then have it be a fistula. I'm not sure what the odds are that he can have this and not have Crohn's?

My Mother is sick with worry, as this would just be much too hard to deal with. He's on a lot of medication as it is, a lot of it to keep him calm. Can you imagine what Prednisone would do to him? Not to mention he would not understand what's going on, and well he's life quality is already not that great. Given his situation, he isn't capable of more then maybe the life of a 2 year old. It's incredibly sad.

I told her however to not jump the gun. Maybe it was just an abscess, and now that it drained maybe it will just heal. But down deep I worry as that's exactly what mine did. Only it never healed and I had a fistula and Crohn's. Any thoughts?

Thanks Ides. I sure hope there is another reason for it. He has a lot of constipation (most of my family does, I'm the exact opposite of everyone). So maybe something like that caused it. I know my Mom is still very upset, not that I can blame her. But we have to stay hopeful that he's not going down my road. Thanks again.