In what could raise hopes of thousands of families, scientists have managed to halt a rare brain disease that kills boys by the time of adolescence through an experimental gene therapy.

During the treatment, the team of doctors used a virus known as a lentivirus -- a disabled form of HIV -- to deliver working genes into two Spanish boys suffering from X-linked drenoleukodystrophy (ALD), a common form of brain disease that affects boys at an early age of six.

"This gives children with ALD and their families the hope of a future," said Patrick Aubourg, Professor of Paediatrics at Paris Descartes University, who led the research.

"The treatment may also be suitable for adults with a late-onset form of the condition," he hoped.

The disease, which was featured in the 1992 academy award-winning movie 'Lorenzo’s Oil', affects one boy in 20,000, and is caused by a mutation in the ALD gene, leading to the loss of protective myelin coverings from nerve cells, Times Online reported.

In about 55 per cent of cases, symptoms start between the ages of 6 and 8, causing brain damage and death by the teenage years. The remaining 45 per cent of male carriers develop a less severe form in adulthood, though this can still cause brain damage, paralysis and death.