A woman in Scotland can feel virtually no pain due to a mutation in a previously-unidentified gene, according to new research.
She also experiences very little anxiety or fear, and may have enhanced wound healing.
The pensioner only found out when she was 65 and sought treatment for an issue with her hip which turned out to involve severe joint degeneration although she had experienced no pain.
At the age of 66 she had surgery on her hand at Raigmore Hospital in Inverness and reported no pain afterwards, although the treatment is normally very painful.
Dr Devjit Srivastava, a hospital consultant in anaesthesia and pain medicine, diagnosed her pain insensitivity and she was referred to pain geneticists at University College London and the University of Oxford.
Scientists there conducted genetic analyses and found two notable mutations, one being a "micro-deletion", or a tiny bit missing, in a pseudogene, which do not have the full functionality of regular genes.
The researchers dubbed it FAAH-OUT and also found that the woman had a mutation in the neighbouring gene that controls the FAAH enzyme.
The FAAH gene is well-known to pain researchers, as it is involved in endocannabinoid signalling which is central to pain sensation, mood and memory.
Scientists have found that mice that do not have the FAAH gene have reduced pain sensation, accelerated wound healing, enhanced fear-extinction memory and reduced anxiety.
The woman, who wished to remain anonymous, experiences similar traits.
She said that throughout her life she often didn't notice cuts or burns until she could smell burning flesh and the injuries tended to heal very quickly.
She was given the lowest score on a common anxiety scale, and told researchers that she never panics, even in dangerous situations such as a recent traffic incident.
The pensioner also reported memory lapses throughout life such as forgetting words or keys, which has previously been associated with enhanced endocannabinoid signalling.
She said: "I had no idea until a few years ago that there was anything that unusual about how little pain I feel - I just thought it was normal. Learning about it now fascinates me as much as it does anyone else.
"I would be elated if any research into my own genetics could help other people who are suffering.
Dr James Cox of UCL Medicine, one of the lead authors of the paper, said: "We hope that with time, our findings might contribute to clinical research for post-operative pain and anxiety, and potentially chronic pain, PTSD and wound healing, perhaps involving gene therapy techniques."
