The disease (as you may logically conclude from what I said) is specifically named in the books. So it is not "some disease" (unspecified) nor "catomisia"
(something whose name you just make up without any support for it in the text) but something named in the book.
Okay, another hint (though I am not sure if it will help or if it will confuse things more
If it seemed confusing to you, you would perhaps do better by ignoring it): There was a certain group of inhabitants of M-E who all had this disease by default. (This person, who is the subject of the question, was not one of them, though.)