A teacher from south-west England has beaten ME and now intends to take on two marathons in two weeks to help other sufferers.
Christina Conner from Cheltenham, Gloucestershire, had the condition for five years and was bedridden for three, but has since managed to get her life back on track - a fact she intends to prove at this year's London and Paris marathons.
Ms Conner told the BBC: "I want to put a story through that, for the person lying in bed at the moment, provides a glimmer of hope.
"[I want] people to see that you can do it - you can go on and have a normal life."
People with ME experience chronic fatigue and muscle pain, while the condition also impairs the body's immune system.
Ms Conner will be running in aid of charity Action for ME, which was established in 1987 with the purpose of improving the lives of people with the condition.