If you’ve never heard of body identity integrity disorder, or BIID, then this first-person article will be a mind-blower.

BIID is a psychological disorder in which the sufferer, who is usually "normal" in all other respects, does not "identify" with certain parts of his or her body.  This usually manifests itself in childhood, and carries into adulthood, when the sufferer longs for amputation.  Here’s how the article begins:

I was six when I first became aware of my desire to lose my legs. I don’t remember what started it – there was no specific trigger. Most people want to change something about themselves, and the image I have of myself has always been one without legs.

To the general public, people like me are sick and strange, and that’s where it ends. I think it is a question of fearing the unknown. I have something called body identity integrity disorder (BIID), where sufferers want to remove one or more healthy limbs. Few people who haven’t experienced it themselves can understand what I am going through. It is not a sexual thing, it is certainly not a fetish, and it is nothing to do with appearances. I simply cannot relate to myself with two legs: it isn’t the "me" I want to be. I have long known that if I want to get on with my life I need to remove both legs. I have been trapped in the wrong body all this time and over the years I came to hate my physical self.

More from wikipedia:

Symptoms of BIID sufferers are often keenly felt. The sufferer feels incomplete with four limbs, but is confident that they will feel better about this post-amputation. The sufferer knows exactly what part of which limb should be amputated to relieve their suffering. This is commonly an above-the-knee amputation. The sufferer has intense feelings of jealousy toward amputees. They often pretend, both in private and in public, that they are an amputee. The sufferer recognizes the above symptoms as being strange and unnatural. They feel alone in having these thoughts, and don’t believe anyone could ever understand their urges. They may try to injure themselves to require the amputation of that limb. They generally are ashamed of their thoughts and try to hide them from others, including therapists and health care professionals.

The women in the above article eventually married, and over time, revealed her desires to her husband.  It took years for him to understand.  Eventually, after some attempts to remove one of her legs on her own, she was able to find a surgeon who was willing to amputate her left leg, just above the knee:

I already feel more complete now that one leg is off. I have always been an outgoing kind of person, but my confidence is much higher now as my body is more like I want it to be. For the first time I feel able to move on and lead the life I have always wanted. In many ways I am starting again. I know it sounds odd, but it is incredibly exciting. Running the house, doing the gardening, going shopping – these are all things I manage easily by myself, even though now I might use a wheelchair or crutches. My husband has been supportive. He thinks I look a little strange missing a leg but says that, after all he has seen me go through, he accepts it. For now, he is just happy that I am happy, and I have promised to leave the remaining leg on for as long as possible; I know that losing that will be really difficult for him.

She writes optimistically about the day her other leg will come off.

Because of the taboos associated with this psychological phenomenon, it is unknown how many people actually suffer from BIID.  And nobody is sure what causes it.

There are, of course, associations formed to deal with this problem, and a variety of therapies.  Surprisingly, one of those therapies is quite simple, albeit very controversial: giving the patient what he/she wants by surgically removing the offending body part.