PARIS — A breakthrough mix of stem cell and gene therapy halted a lethal brain-wasting illness in two young boys, and could prove effective against other genetic disorders, researchers reported Thursday.

The boys, both seven when treatment began in France, are beset with X-linked adrenoleukodystrophy, or ALD, a hereditary brain disease that slowly strips away layers of fatty acids protecting nerve fibres in the brain.

Without treatment, ALD -- which only strikes males -- results in a downward spiral of physical and mental disability, and finally death. Few patients reach adolescence.

The disease's terrible toll was depicted in the 1992 film "Lorenzo's Oil", the true story of an American couple's tireless struggle to find a cure for their son.

"This is the first time that a very severe brain disease has been treated with efficacy by gene therapy," said lead researcher Patrick Aubourg, a professor of paediatrics at University Paris-Descartes.

Up to now, ALD patients were given bone marrow transplants, a technique hampered by the scarcity of donors and the risk of serious complications.

In the new treatment, bone marrow stem cells were harvested from the patients -- the boys, in effect, became their own donors.