A new stem cell treatment hailed as "miraculous" by doctors reboots the entire immune system and is enabling multiple sclerosis sufferers to walk, treat run and even dance again.
Patients who have been wheelchair-bound have regained the use of their legs; others who were blind can now see.
The treatment is the first to reverse the symptoms of MS, health which is considered incurable.
The two dozen patients who are taking part in the trials at the Royal Hallamshire Hospital, in Sheffield, northwestern England, and King's College Hospital, London, have to all intents and purposes had their immune systems "rebooted".
Although it is not known what causes MS, some doctors believe that it is the immune system itself that attacks the brain and spinal cord, leading to inflammation, pain, disability and, in severe cases, death.
In the new treatment, a high dose of chemotherapy is used to knock out the immune system before it is rebuilt with stem cells taken from the patient's own blood.
"We have seen profound neurological improvements," Basil Sharrack, a consultant neurologist, said.