Table 4. Common Genetic Syndromes Associated With Hamartomatous Polyps
|Syndrome||Gene||Gene Function||Hereditary Pattern|
|Cowden syndrome||PTEN ||Tumor suppressor||Dominant|
|Juvenile polyposis syndrome||BMPR1A, SMAD4, ENG||Tumor suppressor||Dominant|
|Peutz-Jeghers syndrome||STK11||Tumor suppressor||Dominant|
Familial polyposis is inherited as a dominant trait, which confers a high degree of risk. Early diagnosis and surgical removal of the colon eliminates the risk of developing carcinomas of the large bowel. Some colorectal carcinomas in young people, however, may be associated with a mutation of the adenomatous polyposis coli (APC) gene, which also is associated with an increased risk of brain tumors and hepatoblastoma. The familial APC syndrome is caused by mutation of a gene on chromosome 5q, which normally suppresses proliferation of cells lining the intestine and later development of polyps. A double-blind, placebo-controlled, randomized phase I trial in children aged 10 to 14 years with familial adenomatous polyposis (FAP) reported that celecoxib at a dose of 16 mg/kg/day is safe for administration for up to 3 months. At this dose, there was a significant decrease in the number of polyps detected on colonoscopy.[Level of evidence: 1iiDiv] The role of celecoxib in the management of FAP is not known.
Another tumor suppressor gene on chromosome 18 is associated with progression of polyps to malignant form. Multiple colon carcinomas have been associated with neurofibromatosis type I and several other rare syndromes.
Presenting symptoms are nonspecific and include abdominal pain, weight loss, change in bowel habits, anemia, and bleeding; the median duration of symptoms was about 3 months in one series.[71,74,97] Changes in bowel habits may be associated with tumors of the rectum or lower colon. Tumors of the right colon may cause more subtle symptoms but are often associated with an abdominal mass, weight loss, decreased appetite, and blood in the stool. Any tumor that causes complete obstruction of the large bowel can cause bowel perforation and spread of the tumor cells within the abdominal cavity.
Diagnostic studies that may be of value include examination of the stool for blood, studies of liver and kidney function, measurement of carcinoembryonic antigen, and various medical imaging studies, including direct examination using colonoscopy to detect polyps in the large bowel. Other conventional radiographic studies include barium enema or video-capsule endoscopy followed by computed tomography of the chest and bone scans.[84,87,98]