Two rare gene variants have been discovered in a Scottish woman who lives a virtually pain-free life.
Seventy-one-year-old Jo Cameron has experienced childbirth, multiple surgeries and minor injuries with hardly any experience of pain or need for pain relief. When she needed a hip operation, consultant anaesthetist Dr Devjit Srivastava – a co-author on the paper – noticed her pain insensitivity and referred her to geneticists at University College London and the University of Oxford.
'We found this woman has a particular genotype that reduces activity of a gene already considered to be a possible target for pain and anxiety treatments,' said study author Dr James Cox, of UCL. 'Once we understand how the new gene works, we can think about gene therapies that mimic the effects we see in her. There are millions of people living in pain and we definitely need new analgesics.'
The study, published in the British Journal of Anaesthesia, describes two changes to Cameron's genome which the researchers think are responsible for her pain insensitivity. One is a small deletion in a gene called FAAH. The second is a change in a newly identified gene, FAAH-OUT, which scientists believe acts to control the amount of FAAH.
Both genes are involved in regulating levels of a chemical called anandamide. Sharing similar effects to cannabis, anadamide is made naturally in the body and plays important roles in memory, fear and pain perception. It has also been related to conditions such as anxiety and depression. Cameron has twice as much anandamide as the average person, which study authors believe may be a result of the two mutations. She also has accelerated wound healing and very little anxiety.
Cameron's astonishing lack of pain response was only noticed by doctors when, despite extreme deterioration of her hip joint, she felt no pain, and only approached doctors when she was unable to walk.
'I had no idea until a few years ago that there was anything that unusual about how little pain I feel,' said Cameron. 'I just thought it was normal.'
The authors believe there may be others with similar mutations who are also unaware of their condition, and urged people who experience less pain to come forward. 'People with rare insensitivity to pain can be valuable to medical research as we learn how their genetic mutations impact how they experience pain,' said Dr Cox.