A new clue to endometriosis, a painful and poorly understood disease

Emerging research points to a possible link between endometriosis, a chronic disease that causes debilitating pain, and bacteria commonly found in the mouth and gastrointestinal tract.

Endometriosis has baffled physicians for years. The condition affects roughly 10 per cent of women worldwide and around one in nine women in Australia. Scientists have theorised about possible triggers, but for now, the root cause is largely unknown, which means treatment options are limited.

Endometriosis is a condition in which tissues similar to those in the uterine lining grow outside the uterus.Credit: iStock

In a study published on Wednesday in the journal Science Translational Medicine, Japanese researchers examined vaginal swab samples from 155 women – 76 healthy women and 79 women with endometriosis. They found that 64 per cent of the women with endometriosis tested positive for bacteria in the genus fusobacterium in their uterine lining, while less than 10 per cent of the healthy women carried the bacteria there.

After the initial discovery, researchers used mouse models to investigate the link further. They found an increase in endometriotic lesions after injecting mice with fusobacterium. When they gave antibiotics to the mice, the lesions’ number and weight declined significantly.

Some strains of fusobacterium are harmless, but others can cause severe infections in humans. Fusobacterium are associated with oral diseases such as periodontitis and tonsillitis, but this is the first time the bacteria have been linked to problems with the female reproductive system.

Yutaka Kondo, one of the study authors and a cancer biologist from Nagoya University Graduate School of Medicine in Japan, described the discovery as groundbreaking in the field of women’s healthcare.

“Previously, nobody thought that endometriosis came from a bacterial infection, so this is a very new idea,” Kondo says.

Endometriosis is a condition in which tissues similar to those in the uterine lining grow outside the uterus. The lesions cause excruciating menstrual cramps and digestive issues and can lead to infertility. Previous research attributed the affliction to retrograde menstruation, a genetic predisposition or hormones, though no one knows the exact cause.

The contraceptive pill, a hormonal option that stops a person’s menstruation, is one of the treatments for endometriosis. But it is only effective when a person is taking the pill. Once they stop the medication to try to get pregnant, the pain resumes. And since 30 to 50 per cent of people with endometriosis experience infertility, they are likely to spend months trying to get pregnant while living in excruciating pain.

The only “cure” for endometriosis is removing a person’s reproductive organs.

“Medicine puts a Band-Aid on it,” says Allison K. Rodgers, a reproductive endocrinologist at the Fertility Centres of Illinois who was not involved with the study.

“I can give you medicine to stop your periods; I can give you birth control pills; I can give you pain meds; I can cut it out with surgery,” she says. “But we haven’t figured out the why, and once we start figuring out the why, we’ll be able to design targeted approaches for treatment.”

Kondo emphasises that while no conclusive treatments can be derived from this new study, he hopes the discovery will ignite research into more potential therapies.

“If this indeed holds true for other patients, it may be worth investigating the microbiome of patients with endometriosis from a larger population and assessing whether there’s a mix of different infectious agents that cause inflammation and change the tissue to behave like endometriosis,” says Raymond Manohar Anchan, director of the Stem Cell Biology and Regenerative Medicine Research Laboratory at Brigham and Women’s Hospital in Boston.

Anchan, who specialises in endometriosis, says that he would be “surprised” if this were a complete correlation and that it “warrants more investigation”.

Anchan and Rodgers also note that the sample size is small, and say the study results would not warrant patients being automatically prescribed antibiotics to treat their endometriosis.

Still, Rodgers similarly describes the results as “exciting, even though they’re in their infancy”. She and other experts believe it is a jumping-off point for further research.

”Studies like this are exciting – for every 1000, probably only one goes on to make a giant discovery,” Rodgers says. “But once we can figure out why some people’s endometrial cells are extra sticky, we can look at targets for a cure.“

Washington Post

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