Researchers are close to identifying the gene responsible for an inherited disorder in which a simple inability to break down and dispose of certain fats can kill seemingly healthy boys.

As the researchers close in on the gene, they are testing a specially formulated diet that may prevent the appearance of the disease in boys and men who have inherited the genetic defect, said the leader of the research team, Dr. Hugo Moser of Johns Hopkins University in Baltimore.The discovery of the gene may allow researchers to insert normal cells into the victims' bodies to cure the disorder, in which apparently healthy boys suddenly lose mental faculties, go into a coma and die.

Moser said Thursday at a genetics meeting at the Jackson Laboratory in Bar Harbor, Maine, that the disease, which occurs in perhaps one in 10,000 or one in 20,000 people, has a devastating effect on families.

In its most severe form, it usually strikes boys 4 to 8 years old, Moser said. They deteriorate to a vegetative state within a year, and they remain in that state for up to 10 years before dying, he said.

"You can imagine what that does to the family," he said.

Before the disease appears, the boys have no signs of illness, he said.

One boy lost the ability to distinguish speech early in the disease and could understand his mother only by reading her lips. Shortly after Moser determined this, he got a call saying the boy had lost his vision - and with it the ability to communicate with his mother.

"Somehow the devastation of a normal child is even harder to take than a child that is born impaired," Moser said.

In people with the disorder, the abnormal build-up of these fats, which are called long-chain fatty acids, damages the adrenal gland, causing hormonal problems, and the insulation surrounding nerve cells, causing brain damage.