A friend of mine's dd has got this - she's 4 now and has had it since she was born - was in fact born by emergency section at about 34 weeks as they picked it up at that point.
She's fine but is on medication and seen regularly I think at hospital. Very recently they tried getting her off the medication as I think children can sometimes grow out of it, but she had another episode so she's back on it.
I think an operation's being talked about for her as well, but for the moment she's fine - has started school, is perfectly happy and healthy in every other respect.