Children's Hospital of Philadelphia researchers say the responsible gene might be a "master switch" that helps turn on the debilitating disease.

The scientists reported on the link between the gene region and juvenile idiopathic arthritis, formerly called juvenile rheumatoid arthritis. The genetic variant is on chromosome 9 in a region housing two genes, TRAF1 and C5.

The TRAF1 gene codes for a protein that regulates tumor necrosis factor, a chemical strongly associated with JIA. However, the researchers say further study is needed to determine whether the TRAF1 gene or the C5 gene is altered in the disease.

"There are only a few genes that may act as master switches like this to regulate autoimmune diseases," said Drs. Terri Finkel, Hakon Hakonarson and Edward Behrens. "This switch we discovered probably has to be an 'on' gene and when it interacts with other genes and environmental triggers, a child may get juvenile arthritis."

The study appears in the journal Arthritis & Rheumatism.