Understanding Endometriosis: What Are Phenotypes?

Each person’s experience with endometriosis can be very different. Some have severe, daily symptoms, while others have minor signs. Even treatment response can vary widely. One drug or surgery may be helpful for 1 endo warrior and have no effect on another. The reasons for this are not well understood. Learning more about different experiences with endometriosis is becoming more important than ever.

Current system for staging endometriosis

The American Society for Reproductive Medicine created a staging system for endometriosis. The stages range from 1 to 4. A person is staged during surgery. When looking inside the pelvis, a surgeon can determine where endometriosis lesions occur and how much of the body is affected.¹

Stage 1 refers to mild endometriosis. People with stage 1 have few endometriosis lesions and no significant scar tissue (adhesions). In contrast, people with stage 4 have severe endometriosis. These people have endometriosis tissue all over the pelvis, ovarian cysts, and adhesions. Stages 2 and 3 fall in between.¹

Stages do not always predict symptoms

Although the staging system is helpful, it has its limits. For example, stages do not always align with symptoms. A person with stage 4 endometriosis may have minimal or no symptoms. However, a person with stage 1 could have severe symptoms. The stages do not predict what types of symptoms a woman has or how she will respond to different treatment options. This is where phenotypes may be helpful.¹

What is an endometriosis phenotype?

We all have many genotypes and phenotypes. A genotype refers to our genes (DNA). Our DNA carries instructions for different traits, like having blue versus brown eyes.

A phenotype is what is actually observed or experienced outside of the body. Even though 2 people may have genes for blue eyes, the shades of blue seen by others may be slightly different. Our phenotype is what we actually experience. It can be influenced by genes and the environment.

Sometimes genotypes and phenotypes align. Other times, like in endometriosis, they do not. For example, 2 people may have genes that cause or increase their risk for endometriosis but have completely different symptoms or severity. Phenotypes in endometriosis might be separated by severity of pain, location of pain, fertility, response to treatment, and more.

Why might phenotypes be helpful?

Creating groups based on experiences rather than surgical staging may be helpful in understanding different outcomes. It might also help create guidelines for treatment. For example, 1 phenotype might respond better to surgery versus hormonal drugs. This may help doctors plan more effective treatment.¹

What does the research say?

In 1 study, more than 4,300 women with endometriosis used a smartphone app to track their experiences over 2 years. The app asked broad check-in questions each day as well as more specific questions. Examples included location and severity of pain, period characteristics, and sexual activity. The app also asked about other symptoms (including bladder and bowel issues). Participants answered questions about treatment and daily activities like working and socializing, too.¹

The researchers created 4 different groups with similar experiences. These became phenotypes A, B, C, and D. Highlights of each phenotype include:¹

• Phenotype A – Most likely to have severe pain. Women in this group also had other intestinal or urinary issues as well as pain with sex. For treatment, this group often underwent surgery and used stronger drugs for pain called narcotics. Additionally, their periods were more likely to be heavy, painful, and irregular. Finally, their pain was most likely to be nauseating, deep, burning, or throbbing. Overall, quality of life was lower in this group.
• Phenotype B – Often had light menstrual cycles and good quality of life. Pain in this group was mostly in the pelvis and rated as moderate. People in group B were more likely to use hormonal drugs for their endometriosis.
• Phenotype C – This group was similar to B in that their pain was usually moderate and in the pelvis. However, this group tended to have regular periods and sometimes reported upper abdominal and chest pain alongside their pelvic pain. Phenotype C reported a good quality of life and minimal treatments used.
• Phenotype D – Women in group D had moderate pain that was often broad. These women used a variety of different treatment options. They also reported lighter periods. Women in group D were more likely to have chronic fatigue and anxiety disorders along with endometriosis.

Based on this information, what would you consider your endometriosis phenotype? Comment below!

Although the results are interesting, these are only 4 of the many possible phenotypes of endometriosis. Further research can help better classify groups with even more detail. Eventually, these groups may be followed to determine better, more effective treatment options for each experience. This can help tailor treatment to each person and may lead to a faster improvement in endometriosis symptoms.¹