Mutation of gene may shield from Crohn’s

An international scientific team has pinpointed a gene mutation that appears to protect some people from Crohn’s disease.

The finding could pave the way for diagnostic tools and drugs to treat Crohn’s, a chronic inflammation primarily of the small intestine, which afflicts more than 500,000 people in the U.S. Typically diagnosed before age 30, it causes diarrhea, abdominal pain, bleeding and weight loss.

“Once you get it, you pretty much have it for life,” said Dr. Steven R. Brant, director of the Meyerhoff Inflammatory Bowel Disease Genetics Laboratory at Johns Hopkins University and coauthor of the research, published online Thursday by the journal Science.

The condition is widely considered to arise when immune cells assault harmless, naturally resident intestinal bacteria.

In 2001, scientists first identified a major gene, Nod2, underlying Crohn’s disease.

The new finding is the first mutation to be identified that might help protect against Crohn’s.

Scientists examined the DNA of more than 550 volunteers with Crohn’s, looking for tiny variations in more than 300,000 locations along the DNA molecule for genes strongly associated with the condition.

Their strongest hit was a gene that codes for immune cell receptors to interleukin-23 -- a protein that regulates inflammation and helps the body fight bacterial infections.

Healthy people were about four times as likely as patients with Crohn’s disease to have the variation.

That has led researchers to conclude that it is somehow protective.