I'm just wondering, in terms of psychological disorders, is this related to this? Is the desire to be castrated a variation (or a form of) apotemnophilia? Or is it something more kinky (if that's possible)?

Here's my take - and bear in mind that I'm having Genital Reconstructive Surgery done in November, so have a possible insight.

Body Dysmorphia that first becomes apparent at age 5-7 is probably related to an anomaly in the part of the brain to do with "body image". This appears to be related to the hindbrain, so development at 6-7 weeks after conception is the danger period.

I base this on a far more common but more complex set of symptoms, that of severe GID (Gender Identity Disorder), otherwise known as TS, Transsexuality. In this syndrome, whose symptoms usually appear at age 5-7, the brain's structures are misgendered compared with the soma. Basically boy brain in girl body or the reverse, and of course, that's a gross simplification, there's a spectrum, and some parts of the brain can be affected and others not.

In many cases of TS, the body image is affected, and TS people with female brains/minds have real problems dealing with the fact that they have external genitalia. Most TS People with male brains/minds have similar problems dealing with secondary sex characteristics, breasts.

On the other hand, some don't - it's a social issue rather than an issue of personal discomfort, it really depends on the degree of cross-gendering and the timing of the neural development.

For Benjamin Scale Type 6 "High Intensity" Transsexual women who are unable to transition for whatever reason, self-mutilation can occur, but suicide is far more common. Take it from me, being TS is far worse than anything you can imagine. The interaction of M blood chemistry with an F type brain causes real problems, and they get worse with age. About 33 years after the start of puberty, most crack.
They are the Type 5's. Type 6's usually transition early, or they're dead before 30. Usually dead, I'm afraid, though it is getting better as we understand more about the situation.

As for me - as part of my cracking at age 47, I had a hormonal storm, which made certain external glands not just dysfunctional, but a high cancer risk. This time last year, I had no intention of transitioning, but sometimes a gal's gotta do what a gal's gotta do. It's been educational.

That article resonated far too much.

It's not looking good these days, Zoe.