There's an important factor when it comes to a mental health diagnosis, and it revolves around whether or not the condition causes the subject distress or impairs their ability to function. Being gay or transgender ceased to meet these criteria when folks realised that gay and trans people can be both happy and fully functional, as long as you allow them to nurture their identity rather than expecting them to repress it. Gender dysphoria is still a thing, but it's the unhappiness created by society's expectations of us (and our own expectations of ourselves) to put the whole thing back in the box and just behave in line with accepted societal norms for our birth sex. It isn't being unhappy with your gender identity, it's being unhappy with the way that society treats you if you dare to express it. Someone who can't be happy unless they somehow physically disable themselves has a dilemma. They have to either sacrifice their happiness or their ability to function fully (physically) by self-harming to create the disability. Therefore they still meet the critera of causing themselves either distress or (physical) dysfunction. Therefore it still warrants a mental illness diagnosis. It's like the difference between a fetish and a fetishistic disorder. The former is someone who's turned on by something unusual, and isn't considered a mental health problem. The latter is someone who can only become aroused if that unusual thing is present, and can't function sexually without it. That is a mental health problem. There, I think, is the distinction that I would make between being transgender and being transabled. That's why one is perfectly easy to accept, while the other is much more challenging.

Right up there with folks who put themselves in wheelchairs who don't need them. But they feel they belong in them. Some have sought out having their spinal cords severed.
(Puzzles me to pieces?).

Some sort of Dysmorphic you'd think - but why?

I totally get transgendered - I have niece who is. But I don't 'get' these folks. And I've heard them explain it.

Its simply because you don't feel it. I can't get my head around someone who skins animals alive or fucks kids or cuts peoples heads off for a magic man in the sky. it is a quick way to lose weight.

I used to be a psychologist, There is a disorder in which people believe they have an imagined flaw when nothing is wrong with them. There are some people that think they are too ugly to even be seen by others, and nothing is wrong with them at all, it is a mental problem. Maybe the condition you describe in the same family. It also gets called Body Integrity Identity Disorder. It is not clear to scientist whether it is a mental disorder, brain disorder or other. It starts when the person is young, and even if a limb is removed, "they might not feel better" They usually know someone that is an amputee. The medical community does not know much about this condition. [en.wikipedia.org]

Part of my disease causes me to lose perception of where my limbs are in relation to the world. Many times I forget that I have a right leg, because my nerves don't register it is there.

Now this is not the same as that mentsl disorder, but it's similar in that I think there's a proprioception problem in that their brain doesn't fully grasp that they have that limb and it makes them feel wrong TO have it. This is my theory at least.

It is a disorder which has been documented fairly extensively. Unlike transgender, which I don't see as illness, this I do. It draws others--medical professionals--into it.