Study Reveals Why Many Lyme Patients Still Have Joint Pain After Treatment

Many people who have (or suspect they may have) late-stage or chronic Lyme disease end up with debilitating joint pain and even full-blown Lyme arthritis. And for some of these people, symptoms don't fade even with antibiotic treatment. But now, researchers seem to have identified a potential cause—which means more effective treatment may not be far behind.

In a new study published in the Proceedings of the National Academy of Sciences, researchers discovered that as Lyme-causing bacteria (Borrelia burgdorferi) multiplies, it sheds a cellular component called peptidoglycan, which triggers a unique inflammatory response in the body that leads to symptoms of joint pain and Lyme arthritis.

Researchers identified peptidoglycan in samples of synovial fluid (aka joint fluid) from patients with confirmed cases of Lyme disease whose symptoms were not responding to antibiotic treatment. "We can actually detect peptidoglycan in the synovial fluid of the affected, inflamed joints of patients that have all the symptoms of Lyme arthritis but no longer have an obvious, active infection," said study author and assistant professor of biochemistry Brandon Jutras, Ph.D., in a news release.

To confirm that the peptidoglycan was, in fact, capable of contributing to arthritis on its own, researchers purified the synovial fluid samples (to eliminate all other bacterial components) and injected them into mice. Within 24 hours, the mice experienced dramatic joint inflammation—indicating that the peptidoglycan was to blame.

Because peptidoglycan persists in the synovial fluid and is not easily eliminated, the immune system may continue to mount an inflammatory response to it—which is why joint pain may remain even after the Lyme infection is treated with antibiotics. This may be exacerbated by a number of factors, like certain genetic predispositions or the state of the immune system.

This discovery is great news, as it opens up the door for more targeted treatments for late-stage Lyme arthritis symptoms (and potentially other late-stage Lyme symptoms). Jutras and other researchers are now looking into ways to destroy peptidoglycan, or counter the body's response to it.