It's hard to imagine anyone wanting to lose a limb. But for people living with Body Integrity Identity Disorder (BIID), it’s a burning desire that haunts them every day of their lives.

For "John," it's a feeling that has consumed him for as long as he can remember.

“The first thing I can remember was when I was about 4 or 5 years old and in kindergarten — and I remember riding in the subway, and opposite me, one of the kids in the play group had no left hand — that was apparent — and I was really very curious about this… and I got up and crossed the car and tried to put my hand up his sleeve to try and figure out where his hand was,” he told FOXNews.com in an anonymous phone interview.

VIDEO: Watch 'John' Tell His Story

“John” also recalled several other vivid memories including one incident that happened when he was between the ages of 7 and 11.

“I remember two buses going in the same direction, and I was standing by the second bus, and I said to myself, ‘if I just stick my leg under the rear wheel of the bus, it will run over it and it will have to get cut off,’ and then I can remember saying to myself: ‘How will I ever explain why I did this.’”

“John” never went through with it — he eventually went to college and got married. But even now, after 47 years of marriage, he cannot shake the burning feeling of wanting to be an amputee.

“When I see an amputee — when I imagine the amputee — there is this inner pull that says ‘why can’t I be like that?’” he said.

The stigma that BIID carries is tremendous — and as a result, many people end up feeling like they're “living a lie” — not even sharing their desire to amputate a limb with their spouses or loved ones.

"John" only revealed his secret to his wife five years ago.

“As you can understand, my wife was not exactly pleased with finding out that I wanted to get a leg lopped off,” he said.

“She asked me and said ‘you know, you’re a rational man, you should be able to deal with this,’” he said. “And what I answered is that most of the things we hold deep within us – are not rational.”

Most people think anyone who wants to amputate a healthy limb has to be crazy — but John said that is certainly not the case. He said he has seen several psychiatrists, and all of them have concluded that he’s perfectly sane.

“They said there’s nothing else wrong with me — I just have this odd sort of dependency.”

Now in his “senior years,” as he calls them, “John” said he is feeling more pressure to carry out his lifelong desire.

But the fact is — people with BIID are left with very few options.

In 2000, Dr. Robert C. Smith, a surgeon from Scotland, made headlines when he amputated the healthy legs of two patients with BIID He said he was following the Hippocratic Oath by preventing his patients from resorting to more life-threatening options — but the medical community did not agree. Since then, it’s been virtually impossible for a person to find a surgeon willing to do the elective surgery, and many people with BIID have resorted to drastic and dangerous measures to induce amputation.

“I just want to get on with it,” “John” said. “But I want to do it safely. And my wife — who I won’t say accepts it, but is willing to go along with me, also insists — and I think she’s right, that this be done safely.”

John says that having his leg amputated would finally allow him to move on with his life.

“People keep saying you got to be awfully darn sure because there's no going back," he said, "and what I realized, well, maybe a half a year ago, is that if I keep putting it off, there's no going forward.”

VIDEO: Click here to learn more about BIID.

Understanding BIID

Described for the first time in 1977 as apotemnophilia, BIID was originally thought to be a psychological disorder characterized by sexual arousal associated with desire to be an amputee.

“It actually sounds a lot like another condition which we already do recognize called gender identity disorder ― where, for example, people are born as a male, but feel they're really a woman trapped in a man's body,” said Dr. Michael First, a professor of clinical psychiatry at Columbia University in New York City, who has been studying this rare condition since 1999.

"Typically it's more common legs than arms, there are people who want bilateral amputations, and I actually know of someone who has achieved that," he added.

“The idea here is — a lot of these people want to be an amputee in all that means. Which is the life of an amputee, the life of an amputee is wearing — for some amputees at least — wearing a prosthetic,” First said. “It's more functional. These people don't want to be disabled — they want to be a functioning disabled person.”

Through his research, First began to realize that the current classification of these patients as apotemnopheliacs was not truly representative of the disorder’s actual characteristics, so he came up with the name Body Integrity Identity Disorder to describe the condition as an issue of identity, rather than sexual desire.

“Apotemnophelia was not an accurate name because it suggests that the primary motivation is sexual,” First said. “So where there's these people where clearly the primary motivation was an identity issue, I came up with the name BIID sort of as a model as a parallel to gender identity.”

Click here to see the Top 10 Mysterious Diseases.

People often confuse BIID with a similar mental illness called Body Dysmorphic Disorder (BDD) in which sufferers become fixated on a perceived flaw in their appearance or some slight physical abnormality.

But First says the main difference between the two is that people with BIID don’t see the limb they wish to amputate as a flaw in their appearance.

“These people don't feel that it's a limb that needs to be removed because it's ugly and defective in any way, they just feel like it's extra,” First said. “So it's just a sense of discomfort and they just feel like it's not right having it there.”

For people suffering with BIID, the desire to amputate in order to make their physical appearance match their ideal image of themselves often dates back to childhood, and some patients even recall being exposed to an amputee at an early age as the beginning of their compulsion.

“When I did the interview study, I basically interviewed 52 people with this condition and asked them all kinds of questions about how they felt about it, where they thought it began, and virtually everyone said it started somewhere in childhood or adolescence and it's been persistent ever since then,” First said.

There are other people who have no memory of any early exposure to an amputee, they just say “As long as I can remember, I've felt like my leg shouldn't be here,” he added.

But because of the negative stigma attached to BIID, and the medical ethics involved in amputating a healthy limb, people with the condition often suffer in silence well into their later years.

“As people get older and older they start to feel more pressure to either act on it or not,” First said. “People live with this lifelong burning desire to be an amputee, if they're getting older they start getting to some point where they're like, listen I only have 20 years left of life, it’s now or never.”

As for treatment options, First said he always recommends starting with therapy in combination with certain medications — but he admitted the only thing proven to work so far is surgery.

“There's a huge amount of suffering,” he said. “The people I've interviewed with this condition suffer tremendously with this. They spend so much time thinking about it, they're pre-occupied, their life is unsettled, and after they get the surgery, they appear to be perfectly normal again.”

Recognizing BIID

BIID is not recognized in the Diagnostic and Statistical Manual of Mental Health Disorders (DSM-IV-TR), a book published by the American Psychiatric Association and regarded by most of the mental health community as the bible of identified mental illnesses.

But First, as editor of the last two editions of the DSM, is working to change that, in an effort to create a reference for mental health professionals to use in identifying and treating the condition.

“Number one — for the people who have it — there’s a whole issue of labeling something as a disorder, and there are pros and cons labeling,” he said.

“The disadvantage of labeling is stigma. We’re basically saying this is a mental illness — this is a sickness. But the advantage of having it in the book is twofold. It might encourage more work on treatment by getting it on the map and getting therapists and people aware of it.”

But the most important factor is for the patients themselves, First added.

“Every single person who has this has gone through many years of their lives thinking they’re the only person in the world who has this — feeling very isolated. And the moment they realize that what they have, other people have, and it has a name, it’s very, very comforting and it gives them a sense that they’re not alone.”

The Future of BIID

First is currently working on two studies. In one, he’s examining other disabilities to try and define the boundaries of BIID. He wants to find out if the disorder is just about amputation or something wider.

“One of the reasons of doing that is to provide more insight into what this is really all about,” he said. “If this only exists as an amputation — that may be stronger evidence towards the neurological hypothesis that the researchers out in San Diego were matching. But when you start seeing people who want blindness and deafness and other types of disabilities – it suggests a more psychological origin.”

The other study aims to evaluate the effects of surgery.

“People that have had amputations have claimed to be cured — so I’m going to get a hold of these people who’ve had the amputations and find out if this is really true. Hopefully this should provide more insight about whether surgery is really a viable option,” he said.

In the end, First's priority is treatment.

“I think the community of people with BIID are looking ahead to some future where this will become understood and people can accept it in some way — that this is a condition and there is a solution to their problem.”

Click here for more on Dr. Michael First.

Click here for more on BIID.