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Geoffrey Woods found some remarkable people in northern Pakistan — six individuals who simply could not feel pain. Woods, who studies genetic disorders of the nervous system at the Cambridge Institute for Medical Research, UK, believes that their condition is probably different from previously reported examples of insensitivity or indifference to pain. On page 894, Woods and his team reveal that mutations in the gene SCN9A are responsible for the Pakistanis' condition. In doing so, the group has stimulated the search for an analgesic that could play a significant role in pain management.

How do your subjects differ from other cases of pain-perception disorders?

There has been confusion over whether, in fact, this is a separate condition from the hereditary sensory and autonomic neuropathies. Subjects with these neuropathies, for example, are born with a lack of small nerve fibres, which can result in an inability to sweat or to appreciate temperature differences, and they show indifference or insensitivity to pain. But the boy we first knew about in Pakistan has a complete inability to experience pain. He was infamous for putting knives in his arms and walking on burning coals during street fairs — injuries that put him in the hospital, but he never complained.

How rare is the disorder you describe?

It has to be quite rare — not even one per million. Looking through the literature, there have been just a handful of subjects described. We've looked hard and come across only four families.

Can we live without pain?

I think we've realized that pain teaches you how to look after your body, and avoid tissue damage. Risk taking is controlled by how painful something is or isn't. These children have a real problem in their first few years of life because they self-mutilate, sometimes biting through their tongues.

If SCN9A is essential for experiencing pain, is everyone's individual pain threshold related to it?

We've been led to believe that the mouse is a good model organism for studying pain, but mice without SCN9A don't live at all. It could also be that SCN9A is responsible for some of the variation in pain threshold seen among humans.

If this gene leads to a drug therapy, could we exist in a pain-free world?

I'm not sure you'd want to. You'd damage yourself without knowing it. We've been thinking about the potential for reckless abuse of such an analgesic — for example, among competitive athletes who take drugs to avoid pain.