Causes and Risk Factors of Pseudomyxoma Peritonei (PMP)

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Pseudomyxoma peritonei (PMP) is a rare, slow-growing cancer that produces extensive mucus that builds up within the abdomen and pelvis. The exact cause of PMP is not known. There are no obvious familial or environmental links that factor into acquiring this disorder, either.

The most common cause of PMP is appendix cancer, and in rare cases, other types of tumors can cause PMP. In this article, we will look at possible causes and risk factors of PMP.

close up senior woman using hand to touch stomach after feeling pain

Chainarong Prasertthai/Getty Images

Common Causes

PMP normally starts as a slow-growing tumor in the appendix. It is classified as a low-grade mucinous appendiceal neoplasm (LAMN). Rarely, it will develop in other organs, such as the ovaries, bowel, or bladder. It is not known why some tumors cause PMP and others do not.

LAMN is a tumor that starts from the mucin-producing cells in the appendix. These tumors often produce swelling or enlargement of the appendix as the abnormal mucin-producing cells cause the appendix to become filled with a jelly-like substance called mucin.

If the appendix ruptures, the cells may spread in the body cavity and continue to secrete mucin into the abdomen. The buildup of mucin can lead to:

  • Abdominal pain
  • Bloating
  • Changes in bowel function, including bowel obstruction (blockage)

Only about 20% of patients with a mucinous tumor of the appendix develop PMP, so even if you are diagnosed with cancer of the appendix, getting PMP is uncommon.

The average age of onset of PMP is 48 years, which is earlier than other malignancies that occur within the abdomen. Males and females are affected equally.

PMP is rare, developing in about one or three people out of 1 million each year. Its rarity is one of the reasons so little is known about the condition.

What Does the Appendix Do?

The appendix is a small, tube-like organ that is connected to the large intestine. It’s somewhere between 2 and 4 inches in length and is located in the lower right quadrant of the abdomen. There are theories on what the function of the appendix might be, but there’s no definitive answer. This organ isn’t necessary for survival.


Only two cases of family members being diagnosed with PMP have been reported in scientific literature, a pair of siblings. Therefore, family members of people with PMP are not thought to be at an increased risk for developing the condition.

Studies looking into whether people diagnosed with PMP undergo changes to specific genes have been carried out. One study found genetic mutations (changes in DNA sequences) in 80% of patients with PMP.

The small study found mutations in the genes MCL1, JUN, KRAS, and GNAS in eight out of 10 PMP patients. This could have a significant role in both the diagnosing of PMP—a condition that is often not found until it has reached an advanced stage—and the potential for using targeted drugs for treatment.

Lifestyle Risk Factors

The cause of PMP is unknown, and no avoidable risk factors have been identified. 

It is usually not possible to know exactly why one person develops cancer and another doesn’t. But research has shown that certain risk factors may increase a person’s chances of developing any cancer.

These include:

Limiting your exposure to avoidable risk factors may lower your risk of developing certain cancers.


PMP is incredibly rare, and the causes of this slow-growing cancer are still being investigated by researchers. The primary cause is a cancer of the appendix, but there is nothing you can do to prevent this.

A Word From Verywell

Sadly, there is little you can do to prevent PMP, as scientists are still trying to discover the reasons why this rare cancer occurs. As research evolves, however, new ways to test for genes that may be present in PMP are being discovered, which should aid in future diagnosis and treatment.

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6 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  6. Sio, T., Mansfield, A., Grotz, T. et al. Concurrent MCL1 and JUN amplification in pseudomyxoma peritonei: a comprehensive genetic profiling and survival analysisJ Hum Genet 59, 124–128 (2014). doi:10.1038/jhg.2013.132