Genetic Disorder Reference Sheet: Familial Adenomatous Polyposis

November 04, 2021 by Suzanne Mahon RN, DNSc, AOCN®, AGN-BC

Individuals with 10–100+ polyps may have a germline pathogenic variant in the APC gene, placing them at higher risk for developing colorectal, gastrointestinal, and other cancers. The condition is known as familial adenosis polyposis (FAP), and loss of function in the APC gene is the first step in the adenoma-to-carcinoma sequence. Some people have an attenuated form (aFAP), with delayed polyp growth and fewer polyps (see sidebar). As many as 20% are de novo, meaning that they are the first in their family to have an identified pathogenic variant.

Nursing evaluation begins by obtaining an accurate polyp history (i.e., histologic type, number, location, and age of onset), cancer history for the patient and family (i.e., location, type, and age of onset), and assessment of other clinical features. Nurses should identify a history of desmoid tumors (fibrous tumors in the tissue covering the intestines that tend to recur after surgical resection), congenital hypertrophy of the retinal pigment epithelium, dental abnormalities, and thyroid tumors.

Although most individuals with pathogenic APC variants develop colorectal cancer, the number of polyps and time frame depend on the specific variant. Individuals with the variants should begin annual colonoscopy around age 10; consequently, children at risk should be tested for FAP at that age. Screening continues until the polyp burden becomes too high. Total proctocolectomy with ileal pouch–anal anastomosis is the preferred risk-reducing surgery. Use of nonsteroidal anti-inflammatory drugs has been linked to regression of adenomas and decreased polyp burden, but no U.S. Food and Drug Administration–approved chemoprevention agents are available for FAP.

Individuals with a large polyp burden often undergo colectomy at an early age, leading to a lifetime of psychosocial distress from changes in eating and increased toileting or when and how to tell a potential partner about a diagnosis. Many carriers have concerns about reproduction and possibly passing a pathogenic variant to offspring. Oncology nurses can use several resources to support patients and families (see sidebar).

Surveillance is complex. Nurses should encourage patients to consult with their genetics professional annually to ensure that their surveillance and prevention plans are current and evidence based.


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