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GTR Home > Conditions/Phenotypes > Familial adenomatous polyposis 1

Summary

Excerpted from the GeneReview: APC-Associated Polyposis Conditions
APC-associated polyposis conditions include (classic or attenuated) familial adenomatous polyposis (FAP) and gastric adenocarcinoma and proximal polyposis of the stomach (GAPPS). FAP is a colorectal cancer (CRC) predisposition syndrome that can manifest in either classic or attenuated form. Classic FAP is characterized by hundreds to thousands of adenomatous colonic polyps, beginning on average at age 16 years (range 7-36 years). For those with the classic form of FAP, 95% of individuals have polyps by age 35 years; CRC is inevitable without colectomy. The mean age of CRC diagnosis in untreated individuals is 39 years (range 34-43 years). The attenuated form is characterized by multiple colonic polyps (average of 30), more proximally located polyps, and a diagnosis of CRC at a later age than in classic FAP. For those with an attenuated form, there is a 70% lifetime risk of CRC and the mean age of diagnosis is 50-55 years. Extracolonic manifestations are variably present and include polyps of the stomach and duodenum, osteomas, dental abnormalities, congenital hypertrophy of the retinal pigment epithelium (CHRPE), benign cutaneous lesions, desmoid tumors, adrenal masses, and other associated cancers. GAPPS is characterized by proximal gastric polyposis, increased risk of gastric adenocarcinoma, and no duodenal or colonic involvement in most individuals reported.

Genes See tests for all associated and related genes

  • Also known as: BTPS2, DESMD, DP2, DP2.5, DP3, GS, PPP1R46, APC
    Summary: APC regulator of WNT signaling pathway

Clinical features

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Suggested reading

Practice guidelines

  • ACMG SF v3.1, 2022
    ACMG SF v3.1 list for reporting of secondary findings in clinical exome and genome sequencing: A policy statement of the American College of Medical Genetics and Genomics (ACMG)
  • ACMG SF v3.0, 2021
    ACMG SF v3.0 list for reporting of secondary findings in clinical exome and genome sequencing: a policy statement of the American College of Medical Genetics and Genomics (ACMG)
  • ACMG, 2016
    Recommendations for reporting of secondary findings in clinical exome and genome sequencing, 2016 update (ACMG SF v2.0): a policy statement of the American College of Medical Genetics and Genomics.
  • ACG, 2015
    ACG clinical guideline: Genetic testing and management of hereditary gastrointestinal cancer syndromes.
  • ASCO/ESMO, 2015
    Hereditary colorectal cancer syndromes: American Society of Clinical Oncology Clinical Practice Guideline endorsement of the familial risk-colorectal cancer: European Society for Medical Oncology Clinical Practice Guidelines.
  • ACMG, 2015
    ACMG policy statement: updated recommendations regarding analysis and reporting of secondary findings in clinical genome-scale sequencing.
  • ACMG, 2014
    ACMG technical standards and guidelines for genetic testing for inherited colorectal cancer (Lynch syndrome, familial adenomatous polyposis, and MYH-associated polyposis).
  • ACMG, 2013
    ACMG recommendations for reporting of incidental findings in clinical exome and genome sequencing.
  • NSGC, 2004
    Genetic cancer risk assessment and counseling: recommendations of the National Society of Genetic Counselors. (Retired following 2012 Update)
  • ASCRS, 2001
    Practice parameters for the identification and testing of patients at risk for dominantly inherited colorectal cancer--supporting documentation.
  • EuroGenetest, 2011
    Clinical utility gene card for: familial adenomatous polyposis (FAP) and attenuated FAP (AFAP).

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