James Wilkinson Sword said:

But Chronic Fatigue Syndrome isn't a specific disease, it just
means you get tired for no reason. So we can say we have that.
Saying you have Lyme Disease is wrong if you haven't tested for
it specifically.

Actually, I think Chronic Fatigue means you get tired for a reason, where
the doctor's job is to figure out that reason (which is where all the hokus
pokus starts coming in because it's easier to agree with the patient than
it is to tell the patient that the doctor has no idea what the reason is).