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  • • Familial adenomatous polyposis (FAP) (adenomatous polyposis coli) is a rare but important disease because colorectal cancer develops before age 40 in nearly all untreated patients

    • FAP: Autosomal dominant

    • APC gene localized to chromosome 5q21

    • Thousands of polyps (occasionally fewer) of varying size and configuration are present in the colon and rectum

    • Extracolonic manifestations are associated with FAP:

    • -Endocrine adenoma

      -Osteoma

      -Epidermoid cyst

      -Small bowel adenoma

      -Visceral malignancy

      -Desmoid tumor

      -Thyroid carcinoma

      -Hepatoblastoma

    Gardner syndrome: Variant of FAP with polyposis, desmoid tumors, osteomas of mandible or skull, and sebaceous cysts

    Turcot syndrome: Variant of FAP with polyposis and a medulloblastoma or glioma

    • Congenital hypertrophy of retinal pigment epithelium (always bilateral, more than 4 lesions on each side) predicts FAP with 97% sensitivity

    • -This abnormality is present as early as 3 months of age in affected members

    • Polyps begin to appear at puberty

    • Cancer develops in these patients at a mean age of 35 years

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Epidemiology

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  • • Autosomal dominant pattern of inheritance

    • Colorectal cancer develops before age 40 years

    • In a family with FAP, each first-degree relative of an affected patient has a 50% likelihood of inheriting the mutated gene

    • By age 16, about 50% of affected patients have polyps

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Symptoms and Signs

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  • • Most patients are asymptomatic

    • Lower GI bleeding

    • Alteration in bowel habit

    • Crampy abdominal pain

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Imaging Findings

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  • • Lower endoscopy (sigmoidoscopy or colonoscopy) reveals numerous colonic/rectal polyps

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  • • Sporadic polyps

    • Sporadic colorectal adenocarcinoma

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Rule Out

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  • • Colorectal adenocarcinoma

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  • • History and physical exam

    • Flexible sigmoidoscopy/colonoscopy from puberty until age 40 or 50 to be certain the family members do not have polyposis

    • Upper endoscopy for gastroduodenal lesions

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Surgery

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  • • Once polyposis is diagnosed, colectomy indicated

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Indications

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  • • FAP: 100% penetrance develop colorectal carcinoma

    • Abdominal colectomy ("subtotal colectomy") with ileorectal anastomosis: Leaves risk of rectal carcinoma

    • Total colectomy and the ileoanal pouch procedure is preferred for most patients, especially if there are numerous adenomas in the rectum

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Medications

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  • • Sulindac has been reported to induce regression of rectal polyps after ileorectal anastomosis

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Treatment Monitoring

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  • • When FAP is known in a family, the relatives at risk should undergo surveillance endoscopy annually beginning in their middle teens

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Complications

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  • • Recurrence, development of malignancy in unresected tissue (rectal)

    • Extracolonic manifestations

    • Increased risk of visceral malignancy

    • Development of desmoid tumors in mesentery or abdominal wall

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Prognosis

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  • • If the rectal mucosa is excised completely, the risk of subsequent rectal neoplasia is essentially nil

    • Desmoid tumors grow slowly and capriciously, but they prove ...

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