A British woman has amazed medical officials by not being able to feel pain.
After a serious operation at the age of 65, Jo Cameron's doctors suggested she would need painkillers to deal with pain after the surgery.
But when she felt nothing, doctors discovered Cameron had a rare gene mutation which meant she didn't feel pain like most people. Only one other person is known to have the mutation.
"We had banter before theatre when I guaranteed I wouldn't need painkillers," she told the BBC.
"When he found I hadn't had any, [her anaesthetist] checked my medical history and found I had never asked for painkillers."
Two gene mutations simultaneously supressed her pain while encouraging happiness.
Cameron said she thought she had just been incredibly healthy, and even admitted not feeling pain during childbirth.
But pain can be important as an alert that something is wrong.
"It would be nice to have warning when something's wrong - I didn't know my hip was gone until it was really gone, I physically couldn't walk with my arthritis," she said.
Dr Devjit Srivastava, Cameron's anaesthetist, and Dr James Cox have now published a paper in the British Journal of Anaesthesia on the case.
They encourage anyone who does not experience pain to come forward, as their genetic mutations could be studied.