How rare are the rare complications of a chronic disease? Most medical students and postgraduate examination takers will be able to give a long list of complications for most long-term diseases. Certainly, for those looking after patients with that chronic disease, the clinician needs to be well versed in those complications, how to recognise them and what to do about them. Getting an understanding of the incidence of rare events requires large numbers of children with that disease to be able to get a true perspective. Thus, an accurate, well-managed, funded database of all cases can yield a …