Researchers at Oxford University have identified another form of muscle disease.

It is hoped the discovery will lead to new treatment for patients with myasthenia gravis - commonly known as rag doll syndrome because it leaves its victims floppy.

MG is often difficult to diagnose, but a team at the Radcliffe Infirmary has found a second form of the illness. They believe it could help the 20 per cent of sufferers who doctors find difficult to diagnose and are often given inappropriate treatment.

MG occurs when the immune system mistakenly attacks nerves and muscles, and, in severe cases, patients are left wheelchair-bound or reliant on breathing apparatus.

Led by Prof Angela Vincent, the head of the Neurosciences Group at Oxford's Department of Clinical Neurology, the scientists found the new strain affects different antibodies to other sufferers.

She said their findings, which are published in Nature Medicine journal this week, would result in more reliable tests and new drugs.

Prof Vincent said: "Oxford has had a major programme of research underway into MG for 25 years, and we are delighted to have made this discovery, which should rapidly begin to have a positive impact on patient care."