MONTREAL - Montreal doctors say they're the first to identify the genetic defect behind a bone disease that causes tooth decay, brittle bones and spine fractures in young people.

The painful disease is called MDMHB, or metaphyseal dysplasia with maxillary hypoplasia and brachydactyly.

A team at the Shriners Hospital isolated a gene linked to the disease.

"Patients often have yellow teeth and brittle and crushed vertebrae, which can cause a lot of pain," team leader Dr. Frank Rauch said.

His team began looking into the disease in 2003 when one of his patients complained of back pain.

He examined the patient's family, only to find that three other teenagers and two adults suffered the same symptoms.

Suspecting that he was dealing with a genetic disease, Rauch and a team in Toronto ran DNA tests and isolated the RUNX2 gene in all of the family members.

A defect in the gene was causing more of the RUNX2 protein to build up inside the patients' cells.

The findings appear in the latest issue of The American Journal of Human Genetics.

The Shriners team says its research might someday lead to a cure.

For now Rauch is asking people who believe they are suffering from MDMHB to come to the Shriners to undergo a genetic test.

Once diagnosed, doctors can begin a bone-building treatment that's already used on people with osteoporosis.

Researchers also advise parents who think their children might have MDMHB to get them tested as soon as possible.