> undiagnosed Lyme's disease
I dated someone who claimed to have this, and not only was she very involved with ILADS advocacy, she had the Wikipedia page on "Chronic Lyme disease" memorized:
https://en.wikipedia.org/wiki/Chronic_Lyme_disease
Six doctors in a row, including an infectious disease research specialist, diagnosed her with fibromyalgia and recommended treatment, but she wasn't having any of it and kept cycling through doctors in between sleeping the entire day.
I was present in the room when she met one of them. He acknowledged her symptoms, expressed that all of them were strongly consistent with fibromyalgia, and offered to work with her to find a treatment protocol that met her very specific needs. She retorted that "[he was] wrong", and that it had to be due to her Lyme disease that she contracted four years ago. The doctor respectfully replied that the tests he had ordered and description of her symptoms did not support that conclusion, though he understood why she would connect the two (and even acknowledged the "community" of folks who feel that medicine is wrong on this -- he was aware). I watched the session descend into a complete lack of productivity and had to restrain myself from trying to mediate, because she got progressively more frustrated with him not playing ball.
Immediately after we left, she called her mom and told her another doctor had accused her of lying and making her disease up. I can see why she would conclude that, honestly, but it was nonetheless a twisting of the actual narrative. I get it, though: it can be difficult to alter your views or interpret normal interactions correctly when you're positively sure of something, despite it being explained to you as incorrect.
I have listened to her stories, and I've even watched the incidents at hand. Though I only observed one visit, I would bet that not a single medical professional has ever accused her of lying or pretending. They just did not accept her own self-diagnosis. There's a significant difference.