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Juvenile Polyposis Syndrome.

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GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2014.
2003 May 13 [updated 2014 May 22].

Excerpt

DISEASE CHARACTERISTICS:

Juvenile polyposis syndrome (JPS) is characterized by predisposition to hamartomatous polyps in the gastrointestinal (GI) tract, specifically in the stomach, small intestine, colon, and rectum. The term "juvenile" refers to the type of polyp rather than to the age of onset of polyps. Most individuals with JPS have some polyps by age 20 years; some may have only four or five polyps over their lifetime, whereas others in the same family may have more than a hundred. If the polyps are left untreated, they may cause bleeding and anemia. Most juvenile polyps are benign; however, malignant transformation can occur. Risk for GI cancers in families with JPS ranges from 9% to 50%. Most of this increased risk is attributed to colon cancer, but cancers of the stomach, upper GI tract, and pancreas have also been reported. A combined syndrome of JPS and hereditary hemorrhagic telangiectasia (HHT) (termed JPS/HHT) is present in most individuals with an SMAD4 pathogenic variant.

DIAGNOSIS/TESTING:

JPS is clinically diagnosed if any one of the three following findings is present: More than five juvenile polyps of the colorectum . Multiple juvenile polyps throughout the GI tract . Any number of juvenile polyps and a family history of juvenile polyps . Juvenile polyps are hamartomas with a distinct histology that differs from that of adenomas. The genes known to be associated with JPS are BMPR1A and SMAD4. Approximately 20% of individuals with JPS have pathogenic variants in BMPR1A; approximately 20% have pathogenic variants in SMAD4.

MANAGEMENT:

Treatment of manifestations: Routine colonoscopy with endoscopic polypectomy to reduce the risk of bleeding, intestinal obstruction, and colon cancer. When the number of polyps is large, removal of all or part of the colon or stomach may be necessary. Treatment as needed for manifestations of HHT. Prevention of primary manifestations: Cancer prevention/risk reduction through cancer screening. Surveillance: For individuals at risk: monitoring for rectal bleeding and/or anemia, abdominal pain, constipation, and diarrhea; screening by complete blood count (CBC), colonoscopy, and upper endoscopy starting in the mid-teens (age 15 years) or earlier when symptoms occur. In families with the combined JPS/HHT syndrome and/or a known SMAD4 pathogenic variant, predictive molecular genetic testing may be appropriate before age 15 years as surveillance for potential complications of HHT begins in early childhood. Evaluation of relatives at risk: When the family-specific pathogenic variant is known, it is appropriate to perform molecular genetic testing on at-risk family members in the first to second decade of life to identify those who will benefit from early surveillance and intervention.

GENETIC COUNSELING:

JPS is inherited in an autosomal dominant manner. Approximately 75% of individuals with JPS have an affected parent; approximately 25% of probands with JPS have no previous history of polyps in the family and may have the disorder as the result of de novo mutation. Each child of an affected individual has a 50% chance of inheriting the pathogenic variant and developing JPS. Prenatal testing for pregnancies at increased risk is possible if the pathogenic variant in the family is known. Requests for prenatal testing for conditions which (like JPS) are treatable and do not affect intellect are not common.

Copyright © 1993-2014, University of Washington, Seattle. All rights reserved.

PMID:
20301642
[PubMed]
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