U. FLORIDA (US)—Scientists have identified two genetic mutations that cause congenital insensitivity to pain: a condition that affects how strongly pain signals are sent to the brain.

“This is a gene that, depending on how it is modified, has the ability to affect pain sensitivity to a large degree,” says Roland Staud, professor of medicine at the University of Florida.

The findings shed light not just on the inability to feel pain, but also—at least potentially—on cases in which people feel unbearable or chronic pain and could ultimately guide the development of novel and effective pain therapies.

The work is published online and will appear in an upcoming edition of the European Journal of Pain.

Since 2004, Staud has collaborated with geneticists, neurologists, pediatricians, and clinical psychologists to better understand the condition.

The gene in question, called SCN9A, contains a “message” to produce a molecule that acts as a battery to power pain-signaling nerve cells so they can fire impulses.

Mutations that lead to overactivity of that molecule result in severe pain, whereas those that cause the molecule not to function lead to the inability to feel pain.

“If you don’t have this gene it’s like a faint whisper in the wind,” Staud says “Nothing much goes up the nerve, and you don’t feel anything.”

“This is an interesting finding—for many families just knowing that there is a physical cause for an abnormality, in this case a mutation that causes blunted ability to feel pain, can be helpful,” says Stephen Waxman, professor of neurology at Yale University.

“Hopefully by studying patients with these mutations, we will more fully understand the gene’s role in pain signaling and in human pain disorders.”

Waxman was not involved in the study, but has pioneered research on the affected gene.

Insensitivity to pain is rare, and since the first reported case in 1932, only a few others have surfaced.

Pain is a vital survival tool, because it alerts people to damage or potentially harmful situations and also is a key element of emotional experiences such as empathy. Sickness and premature death occur in greater rates among people who are insensitive to pain.

Pain arises from both sensory and emotional stimuli, and involves various nerves and regions of the brain. Sensations or pain come as a result of contact with an object or other stimulus such as heat, when a signal is generated and transmitted to the brain.

While scientists potentially could manipulate genes to allow those affected by the condition to feel pain more readily, they have to weigh the possibility that they might, in the process, set off other conditions such as epilepsy or hypersensitivity to pain.

On the other end, the idea of creating genetic therapies to block pain raises questions about whether doctors should remove a person’s capacity to feel pain simply because he or she requests it.

Researchers are focusing on identifying functional abnormalities associated with the genetic mutations, and ways in which the body compensates.

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