Thursday, December 14, 2006

Congenital Inability To Experience Pain

The latest issue of Nature has this fascinating article about a very rare phenotype- the inability to experience pain. Congenital inability to experience pain can be caused by a single mutation of a gene. This condition causes extreme problems for the people who have this condition. The ability to experience pain is crucial for our survival, it alerts us to injuries, etc. The opening paragraph of this article emphasizes the importance of pain:

Pain is an essential sense that has evolved in all complex organisms to minimize tissue and cellular damage, and hence prolong survival. The onset of pain results in the adoption of behaviours that both remove the organism from a 'dangerous environment' and allow for tissue repair; for example, resting a broken limb so that new bone can form. Pain also protects us from our environment, by teaching us what situations and behaviours are likely to lead to injury. Pain pathways operate at numerous levels in the nervous system and are under both voluntary and involuntary control. Blockade of this system with analgesics has been a major pharmacological achievement.

The study examined families in northern Pakistan, several members of which seemed immune to pain. Here is a brief excerpt that describes the problems some of these children encountered:

The index case for the present study was a ten-year-old child, well known to the medical service after regularly performing 'street theatre'. He placed knives through his arms and walked on burning coals, but experienced no pain. He died before being seen on his fourteenth birthday, after jumping off a house roof. Subsequently, we studied three further consanguineous families in which there were individuals with similar histories of a lack of pain appreciation, each originating from northern Pakistan and part of the Qureshi birdari/clan. All six affected individuals had never felt any pain, at any time, in any part of their body. Even as babies they had shown no evidence of pain appreciation. None knew what pain felt like, although the older individuals realized what actions should elicit pain (including acting as if in pain after football tackles). All had injuries to their lips (some requiring later plastic surgery) and/or tongue (with loss of the distal third in two cases), caused by biting themselves in the first 4 yr of life. All had frequent bruises and cuts, and most had suffered fractures or osteomyelitis, which were only diagnosed in retrospect because of painless limping or lack of use of a limb. The children were considered of normal intelligence by their parents and teachers, and by the caring physicians.

News@Nature also has a story about the article here. That story concludes:

This could offer potential new ways to treat severe pain. Current methods, such as local anaesthetics, are impractical, and constantly taking opiate painkillers can lead to addiction. Targeting SCN9A, perhaps through gene therapy, could also help sufferers of constant extreme pain from injuries, arthritis, spinal conditions or cancer.

But, as the Pakistani subjects showed, the new discovery is of no use in tackling that perennial human condition, emotional pain. "They can blush and cry, and when they have flu they feel unwell," he says. "And they are hurt by rejection just the same as anyone."