Researchers have discovered a gene mutation which prevents the otherwise healthy carriers from sensing pain, after studying three related families with a rare genetic disorder in northern Pakistan.
The research, published today in the journal Nature, provides insight into the mechanics of pain and could lead to the development of more effective pain treatments.
The carriers of the very rare genetic mutation are unable to perceive any form of pain but have otherwise completely normal sensory functions. The initial case study was a ten-year-old street performer in Pakistan with the genetic mutation. His inability to feel pain enabled him to place knives through his arms and walk on burning coals. (The young boy died before his fourteenth birthday from injures sustained after jumping off a roof.)
The scientists subsequently studied six individuals with the genetic mutation from three related families, all originating from northern Pakistan. The six relatives had not experienced pain at any time in their lives. Detailed neurological examinations revealed that there was no evidence of motor or sensory disease, and that they could perceive a number of sensations (including touch, warm and cold temperature, tickle and pressure).
As pain is a survival mechanism which enables organisms to minimise damage to tissues, they had all sustained a variety of injuries, including injuries to their lips and/or tongue from biting themselves when young.
By studying these individuals, the scientists were able to determine that a mutation in the gene SCN9A causes a loss of function in the voltage-gated sodium channel it encodes (subunit Nav1.7). Sodium channels are proteins which excite neurons, and though the precise function of Nav1.7 is unclear, as part of a sodium channel it would play a role in exciting sensory neurons.