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A new report is looking at a potential root cause of endometriosis. FG Trade/Getty Images
  • A new report finds that the painful condition endometriosis may be linked to a bacterial infection.
  • A bacteria called Fusobacterium was found in 60% of women with endometriosis in a study.
  • The findings suggest microbes could play a role in the development of endometriosis, but more research is needed to understand the relationship.

Scientists may have discovered a potential cause of endometriosis, a painful condition in which the uterine lining grows outside of the uterus.

A new report, published in Science Translational Medicine Wednesday, detected a bacteria, called Fusobacterium, in over 60% of women with endometriosis.

The researchers also tested treatments in mice and found that antibiotics targeting Fusobacterium may reduce the size and frequency of lesions associated with endometriosis.

Though the findings suggest microbes could play a role in the development of endometriosis, more research is needed to understand the relationship and whether antibiotics may be an effective treatment in humans.

Endometriosis affects approximately 10% of women, however, the causes are poorly understood.

Researchers hope the findings will lead to new treatment options for people with endometriosis, as the condition is notoriously difficult to diagnose and treat.

“This study showing that there is a potential infectious etiology transforming normal cells into inflammatory cells triggering endometriosis is extremely interesting as targeted antibiotic therapy will definitely contribute to decreasing symptomatic disease,” Dr. David Herzog, the director of gynecology and minimally-invasive gynecologic surgery at Staten Island University Hospital, told Healthline.

The researchers recruited 155 women in Japan — 79 of whom had endometriosis and 76 who did not.

They took vaginal swabs of the participants and found that about 64% of the women with endometriosis tested positive for a bacteria called Fusobacterium.

Of those who did not have endometriosis, 7% tested positive for Fusobacterium.

“The presence of this bacteria in the vaginal swab samples from patients with endometriosis was significantly greater than from patients without endometriosis,Dr. Jane Frederick, a reproductive endocrinologist who specializes in fertility and infertility and Medical Director of HRC Fertility in Orange County, California, said.

The researchers then conducted experiments in mice to further explore if and how Fusobacterium may contribute to endometriosis.

They implanted endometrial tissue from one group of mice into the abdominal cavity of another set of mice.

Within weeks, endometriosis lesions formed in the mice that received the transplanted tissue.

The research team also found that the mice that had also been inoculated with Fusobacterium had more lesions that also tended to be larger.

The researchers investigated whether certain antibiotics, administered vaginally, may reduce the size and frequency of the lesions associated with endometriosis.

They found that antibiotics reduced the amount of Fusobacterium in the mice and appeared to delay the development of endometriosis and shrink the number and size of the lesions.

The researchers say the report suggests antibiotics could be an effective treatment for some cases of endometriosis.

More research is needed to better understand why this bacteria may lead to endometriosis and how antibiotics may help treat the condition.

A clinical trial in women is now being conducted to determine if antibiotics may help with endometriosis.

Dr. Steve Vasilev, a board-certified integrative gynecologic oncologist and medical director of Integrative Gynecologic Oncology at Providence Saint John’s Health Center and Professor at Saint John’s Cancer Institute in Santa Monica, California, says these findings and proposed mechanisms can’t be applied to humans quite yet.

“However, this helps form a solid base of understanding toward unraveling how the microbiome and dysbiosis might lead to the formation and growth of endometriotic lesions,” Vasilev said.

The causes of endometriosis are not known.

“There are many responsible factors, possibly including genetic, immunological and hormonal reasons,” Frederick said.

Many researchers believe that retrograde menstruation — which occurs when menstrual blood period flows upward through the fallopian tubes and into the pelvis instead of out your vagina — contributes to endometriosis, however, many women with endometriosis do not experience this phenomenon.

Though most reproductive-aged women experience retrograde menstruation, only a small percentage (10 to 15%) develop endometriosis.

Per the new findings, other mechanisms, like microbes, may be at play.

“Endometriosis is a multifactorial disease, and its cause is difficult to attribute to a single factor,” says Frederick.

Because the causes of endometriosis are unclear, it can be difficult to treat the condition.

Currently, hormonal medications — like birth control — and surgery to remove the affected tissue are the most common treatments for endometriosis.

“The cause of endometriosis is unknown, which is why this type of research is being conducted,” says Herzog.

Some evidence shows there’s a close link between endometriosis and endometritis, inflammation of the uterine lining, which can be caused by infections.

“This paper connects the opportunistic bacterial species Fusobacterium to this inflammatory state,” says Vasilev, adding that the report also highlights how inflammation might contribute to the genesis of endometriosis.

Fusobacterium has been implicated in oral and gastroenterological infections, and, potentially, with neoplastic conditions as well, says Herzog.

“The bottom line is that any process that inflames ectopic endometrial glands, creating an inflammatory environment, can contribute to the pain and infertility associated with endometriosis,” says Herzog.

New research says a bacteria, known as Fusobacterium, may be a potential cause of endometriosis. The bacteria was detected in over 60% of women with endometriosis, whereas only 7% of women without endometriosis tested positive for it. Per the findings, antibiotics may be an effective treatment for endometriosis, however, more research is needed to better understand the mechanisms behind endometriosis.