Polyposis Syndromes

• • 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

Epidemiology

• • 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

Symptoms and Signs

• • Most patients are asymptomatic

  • Lower GI bleeding

  • Alteration in bowel habit

  • Crampy abdominal pain

Imaging Findings

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

• • Sporadic polyps

  • Sporadic colorectal adenocarcinoma

Rule Out

• • Colorectal adenocarcinoma

• • 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

Surgery

• • Once polyposis is diagnosed, colectomy indicated

Indications

• • 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

Medications

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

Treatment Monitoring

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

Complications

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

  • Extracolonic manifestations

  • Increased risk of visceral malignancy

  • Development of desmoid tumors in mesentery or abdominal wall

Prognosis

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

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