While the "official" definition of BIID includes only a desire for amputation, Dr. Michael B. First, an author of the upcoming DSM-V who first defined BIID has agreed on principle that BIID could include a need for other impairments, such as paraplegia. Anecdotal evidence shows that a large percentage of people who have BIID require different impairments. To confirm this, he is undertaking a new study (as of April 2007), as a follow up to his original study. If it is found the principal motivation of patients with BIID is to have a disability, BIID might be considered to be a form of Munchausen syndrome.
Today, very few surgeons will treat BIID patients by giving them what they want. Some act out their desires, pretending they are amputees using prostheses and other tools to ease their desire to be one. Some sufferers have reported to the media or by interview over the telephone with researchers that they have resorted to self-amputation of a "superfluous" limb, for example by allowing a train to run over it, or by damaging the limb so badly that surgeons will have to amputate it. However, there are few if any cases of actual self amputation of a lower limb recorded in the medical literature. Often the obsession is with one specific limb, and with patients "not feeling complete while they still have a left leg", for example. However, BIID does not simply involve amputation. It involves any wish to significantly alter body integrity. Some people suffer from the desire to become paralyzed, blind, deaf, use orthopaedic appliances such as leg-braces, etc. Some people spend time pretending they are an amputee by using crutches and wheelchairs at home or in public; in the BIID community, this is called the 'pretender'. The condition is usually treated as a psychiatric disorder.
The exact causes for BIID are unknown. However, some experts have put forward theories as to why some people suffer from this illness. One theory states that a child, upon seeing an amputee, may imprint his or her psyche, and the child adopts this body image as an "ideal". Another popular theory suggests that a child who feels unloved may believe that becoming an amputee will attract the sympathy and love he or she needs. The biological theory is that BIID is a neuro-psychological condition in which there is an anomaly in the cerebral cortex relating to the limbs; cf. Proprioception. If the condition was neurological, it could be conceptualized as a congenital form of somatoparaphrenia, a condition that often follows a stroke afflicting the parietal lobe. Since the right side of the inferior-parietal lobule, which is directly related with proprioception, is significantly smaller in men than women, a malfunction of this area could potentially explain not only why men are much more likely to have BIID, but also why the requests for amputations are most often of the left-side limbs (the right side of the brain controls the left side of the body and vice versa). If the condition is similar to somatophrenia, it could have the same "cure" - vestibular caloric stimulation. In simple terms it involves squirting cold water in the patient's right ear.
The vast majority of BIID sufferers are white middle-aged males, although there are some female sufferers as well.
Symptoms of BIID sufferers are often keenly felt. The sufferer feels incomplete with four limbs, but is confident that he or she will feel better about this post-amputation. The sufferer knows exactly what part of which limb should be amputated to relieve the suffering. The most common request is an above-the-knee amputation of the left leg. The sufferer has intense feelings of envy 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.