A 21-year-old man arrived at a hospital and asked for his left leg to be amputated. He had placed it on dry ice for six hours in order to ensure that it would have to be removed. He had longed for it to be amputated ever since he was a little boy.

This is a real case.

Imagine feeling an ever-present, overwhelming desire to remove or incapacitate a healthy part of your body that takes over your life.

Imagine wanting to cut off one of your limbs.

Imagine wanting to cut off both.

Imagine wanting to become blind, deaf or paralysed from the waist down.

People suffering from Body Integrity Identity Disorder (BIID) don’t have to imagine any of this, they suffer it every day. They do not feel their bodies as theirs. They are perfectly aware that their desire is irrational, but they cannot help it. They long for an amputation, but are embarrassed by their need and many times choose to do it themselves.

These patients express their feelings in their own words:

“I can feel exactly the line where my leg should end and my stump should begin. Sometimes this line hurts or feels numb.”

“I feel myself complete without my left leg . . . I’m over-complete with it.”

“The soul feels as though it belongs to a body with only one leg. The body does not correspond to this inner reality.”

“I feel the stump ends in my thighs and a strong ‘desire’ – I don’t have the right word for it – to live with two thigh stumps.”

The rejected limbs are usually the lower limbs, and where only one limb is rejected, it is typically the left

BIID was initially believed to be entirely of psychological origin, but the patients are not delusional, they do not suffer from psychosis and usually present with a normal mental status. Psychological therapy and anti-psychotic drugs do not help the condition, although anti-depressants sometimes do: this is likely because of the enormous distress BIID patients are under.

“The study of BIID is intriguing as it transcends classical neurology,” says Prof Peter Brugger, head of neuropsychology at the University Hospital in Zürich. “We found clear cortical correlates of the disorder, but cannot tell whether the altered behaviour is a consequence or the cause of the structural alterations.”

A study on more than 100 BIID patients revealed that the disorder starts early in life, usually in childhood, and that the majority of those affected are men, representing about 90 per cent of the cases. The rejected limbs are usually the lower limbs, and where only one limb is rejected, it is typically the left.

All these points hint towards a physiological cause underlying the disorder. This was confirmed when some patients who had suffered a stroke or lesions in the right hemisphere of the brain developed BIID symptoms. One stroke patient requested the nurse to remove “that strange leg” from their bed: the leg was indeed the patient’s own.

So if BIID is a neurological disease, where does it come from?

The fact that our body belongs to us is not as self-evident as it would appear: we need it to be represented on our brains. Indeed, scientists believe that our brain possesses an internal scheme, a sort of body map that indicates all the parts that belong in our body. This helps our brain (and us) to distinguish what is ours from external objects.

If the map of our body drawn inside our brain is altered, then there is a marked difference between the internal scheme and our physical body, and conflict arises. When one or more limbs are not present in the scheme, they are perceived as alien. This is likely the origin of that overwhelming desire for amputation, in order to make the physical body match the brain representation.

But not all forms of BIID involve removing offending limbs: some people have a desire for non-functioning limbs. The symptoms are similar but in this case patients long to be paralysed from the waist or the neck down. Curiously, this variant of BIID is more prevalent in women.

An overwhelming desire for blindness has also been reported, although neurologists are not sure whether these patients suffer from BIID. Studies on people affected with this rare disorder have revealed visual overload, ie, stress, fatigue and discomfort arising from visual stimuli.

Similarly, a 36-year-old woman reported a persistent desire to be deaf. She explained that she was hypersensitive to noise and would use cotton wool dipped in oil to plug her ears on a daily basis. For these patients, blindness or deafness would be perceived as relief from overstimulation.

Some scientists still believe that the disorder is of psychiatric rather than neurological origin. “There is no single established cause of this condition,” says Michael First, professor of clinical psychiatry at Columbia University. “For some, there is likely a congenital defect in the part of the brain involved in the mapping of body parts. In others, likely the majority, the causes are psychological and may arise from early childhood identification with, and idealisation of, disabled people.”

Brugger agrees that psychological components might also contribute strongly to the disease: “Social constructions of what is considered a ‘normal body’ may be as important as are neural processes mediating bodily experience.”

Researchers also point out that the number of cases of BIID – although still very rare – has grown exponentially since it was first diagnosed in the 1970s; this pattern is not usually observed with rare neurological disorders, but it is for unusual psychiatric conditions.

However, it is possible that patients with other conditions such as multiple personality disorder identify with BIID. The existence of symptoms of BIID following brain damage, such as in stroke, also points to a neurological component of the disorder.

Because BIID patients understand that their desire is irrational, they mostly keep it secret

It is important to note that BIID sufferers do not appear to seek any perceived benefit associated with disability: their stated aim is solely to feel comfortable inside their own bodies. Because BIID patients understand that their desire is irrational, they mostly keep it secret. This makes it harder to research and is probably one of the reasons why BIID is not officially recognised by the WHO.

It appears no cases have been detected in Ireland to date.

So what can be done for these patients? Their neurological defect cannot be fixed and, as previously mentioned, psychological therapy and psychiatric drugs do not seem to work for them.

Some doctors are openly talking about the possibility of amputation as a treatment.

However, for many doctors, there is no way they would agree to the amputation of a healthy limb.