Six related children in Pakistan have helped scientists to find a genetic mutation that prevents people from feeling pain, a discovery that researchers say could lead to better painkillers.

One of the subjects, anunnamed boy, was a local celebrity in northern Pakistan, where he performed street theatre such as piercing his arms with knives and walking on burning coals.

The boy died after jumping off the roof of a house on his 14th birthday, but DNA from himand members of his clanall showed a genetic defect that prevents a protein from doing its job to signal pain.

The children were all otherwise healthy with apparently normal appearance, hearing, vision and nervous systems, but they were at risk for accidents and undetected illnesses.

For example, they felt no pain from biting themselves. All had injured their lips, and some needed plastic surgery to repair the damage. Two had lost a chunk of their tongues.

In Wednesday's issue of the journal Nature, Geoffrey Woods, a geneticist at the Cambridge Institute for Medical Research in England, and his colleagues say the children carried a mutation in the SCN9A gene.

"The work of Geoff Woods and his team has provided us with an exciting new target for pain killing drugs— potentially this is as important as the identification of the morphine receptors," said study co-author Dr. John Wood of University College London.

The mutation stops a sodium channel that produces nerve impulses that convey pain signals to the brain, which seems to prevent the affected individuals from experiencing pain.

The children show how essential pain is to minimize tissue and cellular damage in complex organisms, the researchers said.

The first published report of someone with a lifelong inability to feel pain was in 1932: a patient who made a living as a human pincushion.

It's not clear how many people have the defect, although it is probably very rare, Woods said.

The drug company Pfizer Inc. has a new pain relief product in preclinical development based on the genetic findings.

With files from the Associated Press