A closer look at Lyme disease.
A closer look at Lyme disease
Recent research suggests that there may be more at work in Lyme disease than a simple bacterial intection. Studies conducted by Allen Steere, MD, of the Tufts-New England Medical Center show that a vast number of people in wooded New England areas have been bitten by ticks carrying the culprit bacterum - and while many of them have developed skin rashes and other symptoms, only a few people have developed the chronic form of arthritis associated with Lyme disease. Dr Steere's work suggests that these people may carry genes that put them at increased risk for this more severe form of the disease.
Lyme disease may include a variety of physical symptoms that appear over time. In initial studies, Dr. Steere and his colleagues found that only a small percentage of people who had early joint symptoms later developed chronic arthritis, defined as continual joint inflammation lasting one year or longer.
Based on these findings, the researchers speculated that something in the physical or genetic make-up of a person could influence the severity and duration of the arthritis. To determine if this might be true, the researchers then studied the genetic types of 80 people with Lyme arthritis. They found that the 58 people who only had occasional bouts of arthritis appeared to have a genetic makeup similar to that of the general population. However, many of the 22 people in the study who had chronic arthritis had the HLA gene types DR3 and/or DR4. They also had long-lasting symptoms that did not respond well to antibiotic therapy.
Researchers already suspect an association between the gene type HLA-DR4 and an increased risk of rheumatoid arthritis (RA). Now Dr. Steere suspects that there may be an association between DR4 and Lyme disease as well.
What makes the study of Lyme disease exciting, though, is that it's one of the few forms of chronic inflammatory arthritis with a known cause. "We know specifically which bacterium is responsible," says Dr. Steere. "So we're looking at what part of that organism might trigger this response and how the bacterium reacts with the person's immune system."
Potentially, answers from studies of Lyme disease may one day help researchers unlock the secrets of RA or other autoimmune diseases.
PHOTO : Children playing in tick-infested areas such as woods and fields are susceptible to tick bites which can transmit the bacterium that causes Lyme disease. Researchers now think that some people may carry genes that put them at increased risk for the more severe form of the disease.