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Condition report · Cancer

Hereditary Mixed Polyposis Syndrome

An inherited condition causing polyps of different types in the large bowel and an increased risk of colorectal cancer. It is caused by changes that increase the activity of the GREM1 gene, including a duplication near the gene.

A condition report looks for rare variants known to cause the conditions it covers.

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The 2 conditions we analyse

Autosomal dominant

Caused by changes that lead to overactivity of GREM1, which normally restrains BMP signalling in the bowel lining. The known cause is a duplication of a noncoding sequence near GREM1 that boosts its expression, originally described in Ashkenazi Jewish families.

Signs and symptoms

Polyps in the colon and rectum of mixed types, usually only a few per colonoscopy, including adenomas, hyperplastic and mixed hyperplastic-inflammatory polyps, often appearing in adolescence or adulthood. Without surveillance, the risk of colorectal cancer is increased. Some families also have extracolonic tumours.

What a diagnosis changes

Regular colonoscopy with removal of polyps as part of surveillance. Genetic counselling and testing of relatives are recommended.

Genes analysed

Also known as

HMPS

Specific forms also covered

  • Hereditary Mixed Polyposis Syndrome 1

    Autosomal dominant

    The GREM1-related form of hereditary mixed polyposis, in which a duplication upstream of GREM1 increases the gene's activity in the bowel lining.

    GREM1

Includes 2 related subtypes ↓
  • polyposis syndrome, hereditary mixed, 1
  • polyposis syndrome, hereditary mixed, 2
MONDO:0011023Orphanet 157794MedGen 1672870Sources: [2][1]

Limitations

  • Known cases are caused by a duplication upstream of GREM1. This copy-number change is not detected by small-variant analysis, so a negative result does not rule out the condition.

References

  1. Plesec T, Brown K, Allen C, A Burke C, Church J, Kalady M et al., 2017. Clinicopathological features of a kindred with SCG5-GREM1-associated hereditary mixed polyposis syndrome. Human pathology
  2. Lieberman S, Walsh T, Schechter M, Adar T, Goldin E, Beeri R et al., 2017. Features of Patients With Hereditary Mixed Polyposis Syndrome Caused by Duplication of GREM1 and Implications for Screening and Surveillance. Gastroenterology

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