Lorenzo Odone lies in a darkened room in his parents' home in Virginia in the United States. He is 16, and his body has matured in the 10 years since he fell ill with a rare and fatal genetic disease, but his mind remains trapped. He cannot see or talk. Communication with those caring for him is so subtle that only his mother and father recognise it, and believe he is aware of what goes on around him.

It is a life - of sorts - but the fact that he is still alive is regarded with amazement by the medical establishment. His parents, Michaela and Augusto, claim that a vegetable oil known as Lorenzo's Oil, which they discovered, is the key to his survival.

Their story was told first in the Independent in 1989 and later in a Hollywood film. Publicity led to hundreds of boys at risk of adrenoleukodystrophy (ALD) being given the oil by desperate parents. Doctors and scientists were dismissive, however, not least because they found it difficult to accept that two non-scientists had discovered a possible treatment for an incurable disease. They wanted scientific proof.

This month, Professor Hugo Moser, a leading neurologist at the Kennedy Krieger Institute in Baltimore, Maryland, presented initial results of a clinical trial of Lorenzo's Oil to an international conference in Edinburgh. Professor Moser described himself as the 'foremost sceptic' of the treatment for ALD. But he told 300 scientists at the meeting of the Society for the Study of Inborn Errors of Metabolism, '. . . the data is strong enough to say that if I had a child (with ALD) I would put him on it.'

Professor Moser, whose work will be published in the American Journal of Metabolic Disease, gave the oil, a derivative of rapeseed, to 139 patients. ALD is a degenerative condition of the nervous system caused by a genetic mutation which leads to the build- up of toxic fat in the body and the destruction of white matter in the brain and myelin, the protective sheath around the nerves. It usually strikes apparently healthy boys between the age of five and 12, starting with behavioural problems followed by a steady deterioration in sight, hearing, and movement, to a vegetative state.

Lorenzo's Oil works by reducing the level of toxic fat in the blood and, presumably, preserving the nervous system. Professor Moser found that boys given the oil lived longer than those not taking it, and the onset of symptoms was delayed in others. Augusto Odone, a former economist with the World Bank, said that the findings confirmed what he already knew: 'Everyone had a hunch that if it was taken in time it could work. The real news is that even if these children take it after the onset of symptoms it works. I am happy that something that bears my child's name gives hope to so many others.'

Further clinical trials in America and Europe are under way to determine how effective Lorenzo's Oil is in preventing ALD in gene carriers who are still healthy. British doctors remain sceptical, and say that all research is complicated by the fact that ALD is variable in onset and format; some carriers never develop it at all, some show symptoms in adulthood and others have very mild symptoms.

For the Odone family the story has moved on. In 1989 Augusto established the Myelin Project, bringing together an international research team of scientists who are working towards the regeneration of myelin. If successful it will benefit a range of conditions.

Meanwhile Augusto and Michaela Odone believe the oil is doing its job and will keep their son alive until they have found a way to restore him to full health. A sequel to Lorenzo's Oil may yet be made.

The Myelin Project, 4 Cammo Walk, Barnton, Edinburgh, EH4 8AN. 031-339 1316.