Gene May Play Role In Back Pain

By Jennifer Brown, Associated Press

PHILADELPHIA, Jul 16, 1999 (AP Online via COMTEX) -- Researchers have identified a mutant gene that may be responsible for some cases of sciatica, a sometimes severe and chronic type of back pain.

The finding could help doctors identify other people at risk.

Back pain has long been one of the most poorly understood disorders, though it affects most adults at some point in their lives.

Sciatica is most often caused by a slipped or ruptured disk, which occurs when the soft material in the center of a disk protrudes from its cartilage container and pinches the sciatic nerve in the spine.

Scientists still believe that obesity, smoking and occupational factors put people at higher risk for sciatica, but this gene may be another factor in about 5 percent of sufferers, said biochemist Dr. Leena Ala-Kokko of MCP Hahnemann University in Philadelphia, who led the study.

''Knowing that you carry this mutation, I would advise these people to avoid these other possible risk factors,'' Ala-Kokko said. ''In finding this gene, we may have put the missing piece in the puzzle.''

The research was published in Thursday's issue of the journal Science.

Another far more common gene defect has also been found that may be responsible for a higher percentage of sciatica sufferers, Ala-Kokko said, though that research has yet to be published.

The mutated gene alters part of an important structural protein inside the disk called collagen IX, preventing it from forming into the correct shape. This makes the disk material too soft and less capable of absorbing the shocks placed on the spine during movement, researchers said. Over time, it begin pressing against the nerve.

''If genetic factors are found to underlie some substantial fraction of cases of sciatica, clearly that would be important,'' said Dr. Richard Deyo, a University of Washington professor of medicine specializing in managing back problems. ''It would change the way we think about the disease and think about risk factors and occupational causes. And hopefully someday help treat it or prevent it.''

The study, conducted with scientists at the University of Oulu in Finland, analyzed the DNA of 180 Finnish patients with sciatica. Nine patients were found to have the mutation, and none of 230 patients in a control group without back pain had it.

Follow-up with four families of the nine patients with the defect revealed a total of 23 relatives with the mutation, all of whom suffered disk problems.