Overview
MSH3-related polyposis is a rare inherited condition caused by changes (mutations) in both copies of the MSH3 gene. It belongs to a group of conditions called constitutional mismatch repair deficiency (CMMRD) or, more specifically, is sometimes called MSH3-associated polyposis or MSH3 polyposis. In this condition, the body's normal system for fixing mistakes in DNA does not work properly. Over time, this leads to the growth of many small polyps — abnormal tissue growths — mainly in the large intestine (colon) and rectum. These polyps are usually the type called adenomas or serrated polyps, and without treatment, some of them can turn into colorectal cancer. People with this condition may also develop polyps in other parts of the digestive tract, such as the stomach or small intestine. The main concern is the high risk of colorectal cancer, which can develop at a younger age than usual. Some individuals may also have a slightly increased risk of other cancers. Because the condition is caused by having two faulty copies of the MSH3 gene (one inherited from each parent), it follows an autosomal recessive pattern — meaning both parents are usually unaffected carriers. Treatment focuses on regular surveillance (monitoring) with colonoscopies to find and remove polyps before they become cancerous. In some cases, surgery to remove part or all of the colon may be recommended. Early diagnosis through genetic testing is very important for managing cancer risk and protecting long-term health.
Also known as:
Key symptoms:
Many polyps (abnormal growths) in the colon and rectumPolyps in the stomach or small intestineRectal bleeding or blood in the stoolChanges in bowel habits, such as diarrhea or constipationAbdominal pain or crampingUnexplained weight lossFatigue or tiredness, sometimes from anemia caused by slow bleedingColorectal cancer, often at a younger age than expectedPossible polyps or growths in other parts of the digestive tract
Clinical phenotype terms (14)— hover any for plain English
Autosomal recessive
Passed on when both parents carry the same gene change; often skips generations
Adult
Begins in adulthood (age 18 or older)
Treatments
No FDA-approved treatments are currently listed for MSH3-related polyposis.
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Specialists
View all specialists →No specialists are currently listed for MSH3-related polyposis.
Treatment Centers
8 centersBaylor College of Medicine Rare Disease Center ↗
Baylor College of Medicine
📍 Houston, TX
🏥 NORDStanford Medicine Rare Disease Center ↗
Stanford Medicine
📍 Stanford, CA
🔬 UDNNIH Clinical Center Undiagnosed Diseases Program ↗
National Institutes of Health
📍 Bethesda, MD
🔬 UDNUCLA UDN Clinical Site ↗
UCLA Health
📍 Los Angeles, CA
🔬 UDNBaylor College of Medicine UDN Clinical Site ↗
Baylor College of Medicine
📍 Houston, TX
🔬 UDNHarvard/MGH UDN Clinical Site ↗
Massachusetts General Hospital
📍 Boston, MA
🏥 NORDMayo Clinic Center for Individualized Medicine ↗
Mayo Clinic
📍 Rochester, MN
👤 Mayo Clinic Center for Individualized Medicine
🏥 NORDUCLA Rare Disease Day Program ↗
UCLA Health
📍 Los Angeles, CA
Travel Grants
No travel grants are currently matched to MSH3-related polyposis.
Community
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Caregiver Resources
NORD Caregiver Resources
Support, advocacy, and financial assistance for caregivers of rare disease patients.
Mental Health Support
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Family & Caregiver Grants
Financial assistance programs specifically for caregivers of rare disease patients.
Social Security Disability
Learn how rare disease patients may qualify for SSDI/SSI benefits.
Questions for your doctor
Bring these to your next appointment
- Q1.How often do I need a colonoscopy, and what should I do if polyps are found?,At what point would you recommend surgery, and what type of surgery would be best for me?,Should my siblings and children be tested for the MSH3 mutation?,Do I have an increased risk of cancers outside the colon, and should I be screened for those too?,Are there any medications or dietary changes that might help reduce my polyp growth?,What symptoms should prompt me to seek urgent medical attention between my scheduled appointments?,Are there any clinical trials or research studies I could participate in?
Common questions about MSH3-related polyposis
What is MSH3-related polyposis?
MSH3-related polyposis is a rare inherited condition caused by changes (mutations) in both copies of the MSH3 gene. It belongs to a group of conditions called constitutional mismatch repair deficiency (CMMRD) or, more specifically, is sometimes called MSH3-associated polyposis or MSH3 polyposis. In this condition, the body's normal system for fixing mistakes in DNA does not work properly. Over time, this leads to the growth of many small polyps — abnormal tissue growths — mainly in the large intestine (colon) and rectum. These polyps are usually the type called adenomas or serrated polyps, and
How is MSH3-related polyposis inherited?
MSH3-related polyposis follows a autosomal recessive inheritance pattern. Genetic counseling can help families understand recurrence risk and testing options.
At what age does MSH3-related polyposis typically begin?
Typical onset of MSH3-related polyposis is adult. Age of onset can vary across affected individuals.