Jo Cameron smells her smouldering flesh before realizing she has even been burnt and scoffs down chilli peppers with ease — and now doctors believe the 71-year-old could hold the key to new treatments for chronic injuries after discovering she feels virtually no pain.

The former teacher has a rare genetic mutation that means she feels less pain, heals faster and experiences less anxiety than most people.

From broken limbs and cuts to childbirth and surgery, Cameron — who resides in Inverness in northeast Scotland — should be no stranger to discomfort.

But for the first 65 years of her life, she was blissfully unaware of her condition.

It wasn't until she underwent serious surgery on her hand that doctors sensed something was amiss.

"When [the doctor] found I hadn't had any [painkillers], he checked my medical history and found I had never asked for painkillers," Cameron told the BBC.

'It would be nice to have warning'

Cameron was referred to pain geneticists at University College London (UCL), who looked into her DNA to determine what made her so unique.

The results, published in the British Journal of Anaesthesia this month, revealed two mutations that simultaneously suppressed pain and anxiety and encouraged happiness, wound healing and memory loss.

The first mutation lessened the activity of a gene called FAAH, which is central to regulating pain sensation, mood and memory.

The second discovery, however, took researchers by surprise.

Its been dubbed FAAH-OUT — and while scientists previously thought it was a "junk gene" that was not functional, they now believe it "mediates FAAH expression."

To put it simply, it acts as a volume control on pain, mood and memory.

As part of her mutation, Cameron has a "microdeletion," which prevents that control from working normally.

"She reported numerous burns and cuts without pain, often smelling her burning flesh before noticing any injury, and that these wounds healed quickly with little or no residual scar," the report noted.

"She reported long-standing memory lapses … she also reported never panicking, not even in dangerous or fearful situations, such as in a recent road traffic accident."

People with rare insensitivity to pain can be valuable to medical research as we learn how their genetic mutations impact how they experience pain. - James Cox

Researchers believe the mutation may have been passed down from Cameron's father, who himself "had little requirement for painkillers."

Further testing revealed that her son also exhibited some signs of pain insensitivity, though the same traits were not observed in her daughter.

For Cameron, the revelation has been enlightening. While able to reflect on events like childbirth as "quite enjoyable really," she believes her condition means she has missed "alarm bells" along the way.

"It would be nice to have warning when something's wrong," she told the BBC.

"I didn't know my hip was gone until it was really gone, I physically couldn't walk with my arthritis."

What the discovery means

Researchers say the discovery could help shine a light on the role of genetics in pain management — and believe there could be more people out there with the same mutation.

"People with rare insensitivity to pain can be valuable to medical research as we learn how their genetic mutations impact how they experience pain," one of the study's lead researchers, James Cox, said in a statement.

Cameron is continuing to work with the research team in order to better understand the pseudogene, including undergoing further tests in cell samples.

Calgary scientist 'shocked'

At Matthew Hill's lab at the University of Calgary, scientists work on the biochemistry of endocannabinoids.

Cameron's blood was tested by Hill, who holds the Canada Research Chair in Neurobiology of Stress. He worked to quantify Cameron's loss of FAAH function.

"When we processed the blood and looked at the data, I was shocked," said Hill, a co-author of the study.

Hill said research on mice lacking FAAH function were insensitive to capsaicin, the component of chili peppers that generates a burning sensation in our mouths.

"I suggested to the doctors that they bring the woman back in and see how she reacted to eating a chili pepper. They brought her back in and had her eat a Scotch bonnet pepper, to which she described as a pleasant tingle."

Overall, Hill called it a fascinating case.

"I think [it] helps us understand even more so how endocannabinoid function regulates pain, emotion and memory in humans and helps to support the future investigation of drugs which target this system as possible therapeutics for the treatment of pain and anxiety," he added in an email.

Devjit Srivastava, co-lead author of the paper, said the findings point towards a novel painkiller discovery that could contribute to post-surgical pain relief and accelerate wound healing.

"We hope this could help the 330 million patients who undergo surgery globally every year," Srivastava said.