What do Marilyn Monroe, Hilary Mantel, Padma Lakshmi, Lena Dunham, Whoopi Goldberg, Cyndi Lauper, Dolly Parton, and Queen Victoria have in common? All of these women are (or were) sufferers of endometriosis, a painful health disorder that affects a woman’s uterus.

Though this chronic disease affects at least 6.3 million women in the United States and millions more worldwide, according to the Endometriosis Association, all too many women do not receive an immediate and correct diagnosis.

When the endometrium, the tissue or mucus membrane lining the inside of the uterus, begins to grow outside the uterus, it's called endometriosis. This misplaced tissue commonly grows in a woman’s ovaries, bowel, or the tissue lining her pelvis, according to Mayo Clinic. In some rare cases, the endometrial tissue may migrate beyond the pelvis to another region of the body.

Wherever it transplants itself, the tissue can develop into growths, which respond to the menstrual cycle as they would had they remained inside the uterus. The misplaced tissue then builds up, breaks down, and sheds. But unlike menstrual blood, which leaves the body after being shed, the blood resulting from out-of-place endometrial growths has no way of leaving the body. Women affected by endometriosis can suffer internal bleeding and inflammation, which can cause scar tissue formation, bowel problems, and sometimes, infertility.

Although some women experience no symptoms, others endure pain and other signs of internal disorder.

“I have constant tummy pains day in, day out that affect my daily lifestyle as they are so bad. I also have been bleeding for the past nine months now. During this time, I have bad episodes where the blood is… just ‘leaking away,’” wrote Joely21 on the Endometriosis UK website.

“I’m also in pain 24/7 and was told by everyone it can’t be Endo as I would only have pain around my period,” replied Feekate.

According to the Endometriosis Association, women who suffer from endometriosis most commonly report pain before and during menstruation that includes pain when urinating or during bowel movements, and pain during sex. It’s also common for women to be fatigued or to suffer gastrointestinal symptoms such as diarrhea, constipation, and nausea. At worst, it can leave those with the disease infertile.

In some cases the pain is relentless. One study sponsored by the World Endometriosis Association Foundation found between 44 and 61 percent of women with endometriosis who had seen specialists or participated in a patient association reported chronic pain, or pain lasting longer than six months. Between 35 and 64 percent reported endometriosis affected their jobs, and between 22 and 52 percent said the disease had impacted their relationships.

Who and Why

Endometriosis is most common in women in their 30s and 40s, though it can happen to any woman who has periods. Women who typically have periods lasting more than seven days, or those who have menstrual cycles lasting 27 days or less, are more likely to suffer from the disease. Endometriosis is more likely to affect those who've never had children, who have a family member with the condition, or a health problem that blocks menstrual flow.

Because endometriosis runs in families, researchers believe it has some genetic foundation, though no one knows for sure what exactly causes the disease. Other scientists believe the immune system may be at fault while others suggest it is a matter of hormones, since estrogen fuels the condition and endometriosis occurs during the childbearing years when estrogen is at a high. Still, it's unclear in all cases what causes the disease.

“Something was scraping and chiseling, urgently, inside my body,” wrote Hilary Mantel, author of Wolf Hall, describing her first period in an article for The Guardian. After going on the pill at age 18, her period pains eased, but then nausea, vomiting, fatigue, and aching legs replaced them, yet “no one added them up.”

In fact, endometriosis, with its mixed bag variety of symptoms, is often met with confusion on the part of health professionals whose help women seek.

“I was offered tranquillizers and antidepressants, and the opportunity of a career as a psychiatric patient, which in the end I found the strength to decline,” Mantel wrote. “Throughout my 20s I sought a diagnosis for increasing debility. Doctors read my notes and wrote me off.” At age 27 she was finally diagnosed, she added, but only while she was under anesthesia on the operating table.

“I had to lose part of my bladder and my bowel, my womb, and my ovaries. I woke up to a strange future — childlessness, a premature menopause, and a marriage, already tottering, that would soon fall apart.”

Browse online chat rooms on the topic and you’ll find that Mantel’s array of symptoms, combined with an incorrect diagnosis, is not unique. In most cases, though, a diagnosis can only be proven by a laparoscopy, a minor surgical procedure that shows the location, size, and extent of the growths.

Relief

As Mantel says, hormonal birth control helps resolve the pain for many sufferers of endometriosis, though not all. Some women who experience extreme pain and other symptoms may undergo surgery to remove the patches of stray endometrial tissue. After surgery, a woman may begin birth control in an effort to prevent the tissue from growing back, though this may not be successful in all cases.

For women who want to get pregnant, the Office on Women’s Health explains, a doctor may prescribe a medicine that stops her body from making the hormones responsible for ovulation and menstruation. By hurling a woman’s body into a temporary menopause, the growth of endometriosis is halted for a spell and her body can heal. The next step begins when the woman stops taking the medicine and her menstrual cycles resume. This method helps better her chances of getting pregnant either naturally or by way of assisted reproductive technologies, such as in vitro fertilization.

For some women, the symptoms will improve after menopause as the growths slowly shrink once the body stops making estrogen. In extreme cases, Mayo Clinic notes, a woman may have her uterus and cervix, as well as both her ovaries, surgically removed.

As with any disease, each woman’s experience is unique and for this reason she needs to become informed about her diagnosis, take part in her own treatment, question her doctors, and find the strength to stick up for herself.

"No one will like me for saying this, but I've often noticed that it doesn’t seem to matter whether a woman goes in for yoga or reiki or dancing on hot coals at the full moon," Mantel wrote. "She starts to get better when she starts to take charge."