Yes, it’s a bona fide fetish/lifestyle. The desire to be an amputee is called apotemnophilia. I’ve seen a few documentaries on it and the brilliant British magazine Bizarre has run a few interesting and fairly in-depth articles on it. Here are the Google and Altavista search results on it - there are thousands of sites devoted to apotemnophilia. It’s really quite widespread.
Obviously, it’s controversial topic and the first rection is usually “Noooooooo way! That’s mentalist behaviour!” but a little research reveals that there are many perfectly rational people who hold these desires, for a wide variety of reasons. And of course, there’s a few mentalists as well. But isn’t there everywhere?
Fran