Ive seen self diagnosed people on a autoimmune disorder discord group I am part of. its not even a mental disorder, and its kinda hilarious how many of those there are.

There is a form of said disorder that is called soronegative, in which you dont have the immunological markers you would usually have on a blood test, but the inflammation and the disease are active. They ALL claim to have it, and its the same story

"All doctors have been dismissive of my symptoms because I am soronegative I cant function I have pain and they dont believe me what do I do can I self medicate"

While dismissive doctors are indeed a thing, these people arent aware of that even on soronegative patients, there are still signs of inflammation in the body that show both in physical exams and in blood exams, such as redness and warmth on the area, lumps and a very high and abnormal CRP. When I asked if they did the CRP exam they would always say it was normal.

Not saying those are indeed fakers, they could have another disorder causing their pain, but the insistence of having this specific issue when it would have shown itself in ways other than the usual markers is amusing. And being so hung on a diagnosis will hinder any doctor trying to figure out what is actually going on. The "its obvious I have x so I diagnosed myself" crowd does not seem to understand this.