Familial adenomatous polyposis is a hereditary disorder causing numerous colonic polyps and frequently results in colon carcinoma, often by age 40. Patients are usually asymptomatic but may have heme-positive stool. Diagnosis is by endoscopy and genetic testing. Treatment is colectomy.
Familial adenomatous polyposis is an autosomal dominant disease in which ≥ 100 adenomatous polyps carpet the colon and rectum.
The disorder occurs in 1 in 8,000 to 14,000 people. Polyps are present in 50% of patients by age 15 years, and 95% by age 35 years. Cancer develops before age 40 in nearly all untreated patients.
Patients also can develop various extracolonic manifestations (previously termed Gardner syndrome), both benign and malignant. Benign manifestations include desmoid tumors, osteomas of the skull or mandible, sebaceous cysts, and adenomas in other parts of the gastrointestinal tract. Patients are at increased risk of cancer in the duodenum (5 to 11%), pancreas (2%), thyroid (2%), brain (medulloblastoma in < 1%), and liver (hepatoblastoma in 0.7% of children < 5 years).
Symptoms and Signs of Familial Adenomatous Polyposis
Many patients are asymptomatic, but rectal bleeding, typically occult, occurs.
Diagnosis of Familial Adenomatous Polyposis
Colonoscopy
Genetic testing of patient and first-degree relatives
Offspring screened for hepatoblastoma
Diagnosis of familial adenomatous polyposis is made by finding > 100 polyps on colonoscopy. Although the characteristic lesions of familial adenomatous polyposis can be recognized on sigmoidoscopy, colonoscopy is usually done to detect a more proximal cancer, which would require evaluation for metastases before treatment.
Diagnosed patients should have genetic testing to identify the specific mutation, which should then be sought in first-degree relatives. If genetic testing is unavailable, relatives should be screened with annual sigmoidoscopy beginning at age 12, reducing frequency with each decade. If no polyps are evident by age 50, screening frequency is then the same as for average-risk patients.
Children of parents with familial adenomatous polyposis may be screened for hepatoblastoma from birth to age 5 years with annual serum alpha-fetoprotein levels and possibly liver ultrasound.
Treatment of Familial Adenomatous Polyposis
Colectomy
Endoscopic surveillance of remainder of gastrointestinal tract
Perhaps nonsteroidal anti-inflammatory drug (NSAIDs)
Colectomy should be done soon after diagnosis. Total proctocolectomy eliminates the risk of colon and rectal cancer. The most commonly used reconstruction options are ileal pouch-anal anastomosis (IPAA) and permanent ileostomy. If subtotal colectomy (removal of most of the colon, leaving the rectum) with ileorectal anastomosis is done, the rectal remnant must be inspected frequently; new polyps must be excised or fulgurated. NSAIDs may inhibit new polyp formation. If new ones appear too rapidly or prolifically to remove, excision of the rectum is needed.
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After colectomy, patients should have upper endoscopic surveillance at periodic intervals. The American College of Gastroenterology's 2015 guidelines for genetic testing and management of hereditary gastrointestinal cancer syndromes recommend doing upper endoscopy including duodenoscopy starting at age 25 to 30 years and repeating surveillance every 6 months to 4 years depending on the stage of duodenal polyposis. The Spigelman classification is used to determine the degree of polyposis based on four variables (number of polyps, polyp size, histology, and dysplasia) and the calculated score provides a recommended surveillance interval (1). Annual screening of the thyroid with ultrasound also is recommended.
Treatment reference
1. Saurin JC, Gutknecht C, Napoleon B, et al: Surveillance of duodenal adenomas in familial adenomatous polyposis reveals high cumulative risk of advanced disease. J Clin Oncol 22(3):493–498, 2004. doi: 10.1200/JCO.2004.06.028
Key Points
Familial adenomatous polyposis is an autosomal dominant disease in which ≥ 100 adenomatous polyps carpet the colon and rectum.
Nearly all patients develop colon carcinoma by age 40, so total proctocolectomy is usually done soon after diagnosis.
Patients have an increased risk of other cancers, particularly of the duodenum, and also the pancreas, thyroid, brain, and liver.
After treatment, patients are screened regularly for other cancers and development of polyps in the upper gastrointestinal tract.
Children of parents with familial adenomatous polyposis may be screened for hepatoblastoma from birth to age 5 years.
More Information
The following English-language resource may be useful. Please note that THE MANUAL is not responsible for the content of this resource.
American College of Gastroenterology: Guidelines for genetic testing and management of hereditary gastrointestinal cancer syndromes (2015)
