For more than a century, scientists have noticed that people with this inflammatory disease are more likely than others to suffer from gum disease. Researchers began to suspect a common factor was triggering both diseases.
"If we're right, this will totally change the view of rheumatoid arthritis and treatment of patients," said study co-author Dr. Felipe Andrade. But cautioned that this is "an early finding that needs confirmation by others."
Rheumatoid arthritis is a chronic form of arthritis linked to an overactive immune system. It can affect a variety of body systems, not just the joints. The disease affects roughly 1.5 million U.S. adults, according to the U.S. Centers for Disease Control and Prevention.
Patients with rheumatoid arthritis had fewer teeth possibly as a result of gum disease. Researchers have also reported that people with gum disease are twice as likely to have rheumatoid arthritis, the study authors said.
"For some time, people thought that people with arthritis didn't have good mobility with their hands and they didn't clean their teeth well," Andrade said.
Andrade's team examined almost 200 samples from the gums of people with rheumatoid arthritis and focused on whether bacteria contributes to both diseases. The researchers looked for evidence of a type of bacteria, called A. actinomycetemcomitans, that's linked to gum disease.
In almost half of the rheumatoid arthritis patients, signs of infection were detected compared to just 11 percent of another group of people without gum disease or rheumatoid arthritis.
This finding raises the possibility that the germ could cause both gum disease and rheumatoid arthritis, the study authors suggested. The bacterium may afflict the gums and then cause swelling in the joints as a kind of side effect.
There is also a possibility about the reverse -- whether gum disease could be a side effect of rheumatoid arthritis. A study published in Current Oral Health Reports raised the question of whether the gums might be, in effect, another affected "joint."
However it may be decades before researchers can actually prove a cause-and-effect relationship between the two. Andrade said that "the findings strongly suggest that antibiotics can be an option for treatment of rheumatoid arthritis."
Still, the finding about the germ involvement "may eventually prove helpful" in the prevention and treatment of rheumatoid arthritis, said Dr. Scott Zashin, a rheumatologist in Dallas.
There have been tremendous breakthroughs in the treatment of rheumatoid arthritis due to the development of biologic-type medications but the cause remains unknown said Zashin.
Zashin said, targeting a bacterium may be especially useful for people who have an increased risk of developing rheumatoid arthritis but haven't developed symptoms, such as family members of rheumatoid arthritis patients. If signs of rheumatoid arthritis were detected early, perhaps treatment could start before these individuals show symptoms, he suggested.
- Felipe Andrade.et al., Aggregatibacter actinomycetemcomitans-induced hypercitrullination links periodontal infection to autoimmunity in rheumatoid arthritis, Science Translational Medicine (2016)
- Mary Anne Dunkin, Rheumatoid Arthritis and Gum Disease, Arthritis Foundation, http://www.arthritis.org/living-with-arthritis/comorbidities/gum-disease/ra-and-gum-disease.php.