Some questions I'm stuck with:

* are all the patients really sick or as sick as the symptoms he documents, or is it some kind of Munchausen induced or lied about by the doctor?

* Or are they all sick, they're just not getting the help they need because he wants to have a mystery disease?

* If they're all sick, is it then a higher prevalence than expected, so even if there is no mystery disease there is still something environmental or similar that should've been explored? Aka, is there a cluster, it's just a known disease?

The prevalence question isn't really answered in the article. If it is 500 cases in an area in which 1m people live then it might not really be a cluster. But if it is 500 cases out of a town of 40000 then it is quite something different.