Familial Adenomatous Polyposis Health Article

Demographics

Approximately one of 8,000 people are affected with FAP. It is seen in all racial and ethnic groups. Both sexes are affected equally.

Colorectal

FAP is characterized by multiple (more than 100) adenomatous polyps of the colon and rectum. These generally develop after the first decade of life but the age of onset of adenomas is variable. Fifteen percent of individuals with FAP will show these polyps by age 10, 75% by age 20, and 90% by the age of 30. More than 95% of affected individuals will have adenomatous polyps by the age of 35. Although these polyps are benign, it is inevitable that, if left untreated, at least one of the hundreds of polyps will eventually progress to cancer. The majority of cancers appear by the age of 40 and over 90% appear by the age of 45. Symptoms of polyps and/or colorectal cancer may include rectal bleeding, change in bowel habits, iron deficiency anemia, or abdominal pain.

Upper gastrointestinal tract

Many individuals with FAP will develop adenomas in the upper gastrointestinal tract as well. The second portion of the duodenum is particularly prone to these polyps. These adenomas are benign, as they are in the colon, but about 5–8% of patients with FAP will eventually develop cancer in this area. Duodenal cancer seems to cluster in certain FAP families while being absent in others. Adenomas of other portions of the small bowel may also occur but with lesser frequency.

In people affected with FAP, benign adenomas can also be seen in the stomach. Gastric cystic fundic gland polyps are also common. These are benign polyps that occur in the fundic gland of the stomach, an organ that secretes enzymes and mucus. It is rare for these polyps to become cancerous in individuals of Western origin. However, in Japanese and Korean families with FAP, the risk of gastric cancer is reported to be increased three- to four-fold over the general population.

Ocular, skeletal, and cutaneous

Approximately two thirds of individuals with FAP will have congenital hypertrophy of the retinal pigment epithelium (CHRPE). These lesions are typically flat, oval, and pigmented. They can be detected by an ophthalmology examination. In FAP patients, these lesions are usually multiple, bilateral, or large. CHRPE does not affect vision nor does it have the potential to become malignant. However, CHRPE is a very important finding for families with a history of FAP. If CHRPE runs in a family with FAP, all or nearly all affected individuals in the family will have this finding. It can be detected at birth and can thus identify susceptible family members at a young age.

Other manifestations of FAP include dental abnormalities, such as impacted teeth, supernumerary teeth, and congenitally missing teeth. Osteomas can occur, often in the jaw area or on the forehead. Soft tissue tumors, such as lipomas, epidermoid cysts, and fibromas, are observed in some patients with FAP as well.

Other tumors and malignancies

Abdominal desmoid tumors occur in approximately 15% of individuals with FAP. Desmoids are tumors made of connective tissue. Although they are not cancerous, approximately 10% grow very aggressively and can become life threatening. They may lead to obstruction of blood vessels, the intestine, or ureters. They may also result in abdominal distention and associated pain and discomfort. Over 70% of these tumors develop in women aged 20–40 years, suggesting a hormonal role in their development. Additionally, they occur more commonly in those who have had prior abdominal surgery. Desmoids may occur as part of classical FAP, as part of Gardner syndrome, or sporadically, without the colonic findings of FAP.

Additionally, patients with FAP are at an increased risk for cancers in organs outside of the gastrointestinal tract. These include brain tumors, thyroid tumors, and hepatoblastoma. Hepatoblastoma is a malignant tumor of the liver and occurs in approximately 1.6% of patients with FAP in the first five years of life. Tumors of the adrenal cortex, biliary tract, and pancreas have also been reported.