The person I know isn't suffering from adjacent illnesses that might be the cause. In the ~30 or so years I've known her she's had:
- too many cancers to count, including leukemia, ovarian cancer, throat cancer, stomach cancer, and lung cancer (not an extensive list because at this point I can't even remember everything)
- lupus
- type 1 insulin dependent diabetes
- Cushings/thyroid disease (also thyroid cancer)
She also makes up incredible and sometimes downright evil stories about herself and the people in her life. To hear her tell it, she was a champion equestrian, graduated from a prestigious university, was a star ballet dancer, slept with any number of famous musicians. The CIA killed her parents. Her mother was murdered for her money. Her husbands (how many? the number changes) were all abusive. (None of this is even remotely true.) Much of this, and the illnesses, was an attempt to gain sympathy to get in with certain groups of people -- prior to social media, it was church groups that she would stay with until her stories started unravelling, after social media it was SO MUCH WORSE.
She had her DC convinced she had all of the above diagnoses and then some, so the day I got the phone call to come collect her younger DS from the hospital as his nearest relative, I found him absolutely beside himself because he thought the staff weren't treating her for her list of conditions. She had been hospitalised due to a painkiller overdose, and was in a coma, so she couldn't speak for herself.
Her DS was shaken to learn that while his mother was certainly very, very gravely ill she did not have cancer, or diabetes, or thyroid issues despite the fact that she medicated for all of it. She used her DS's name and birth information to get prescriptions delivered for pretty much everything -- mostly codeine based painkillers. I had to go to her house, bagging and collecting any pills or medications to bring to the hospital so they could try to unravel what she'd done to herself. Which they eventually did.
To the best of my knowledge she still does all of this. Her DC are now all long over the age of 18 and I can be in contact with them without her, so that's what the family chooses to do. I can only imagine the pattern continues with fake illnesses, wild stories, and finding new groups of people to lie to.