It sounds a little convient for doctors to say people with certain symptoms are delusional since they can't find why they are having the symptoms they are having.
They don't seem to have dillusional cancer or dillusional parkinsons disease. Seems pretty ridiciolous. I don't know if there are people with it or not but you were getting off on arguing with people here recently so I'm not gonna spend my energy doing so.
Also you say of course like you know for sure, but it is a pretty convinient thing for an incompetent physician unable to diagnose patients to call people dillusional.