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Familial Adenomatous Polyposis Definition
A genetic disorder in which hundreds of intestinal polyps grow in the rectum and colon. FAP is an extreme risk for early-onset colorectal cancer. This autosomal dominant disorder results from a defective gene, inherited from one parent, in which there is a mutation of the adenomatous polyposis coli (APC) gene.
The ACP gene regulates the proteins that inhibit adenomas (abnormal growths arising from epithelial cells, the cells that form the surface layer of skin and membranes) in the intestinal mucosa. The mutation of the ACP gene blocks these proteins, allowing adenomas, called intestinal polyps when they occur in the colon, to flourish. In FAP polyps are generally abundant by late adolescence, with colorectal cancer developing before age 40.
Symptoms of Familial Adenomatous Polyposis (FAP)
The rapid and prolific growth of Familial Adenomatous Polyposis (FAP)-associated intestinal polyps significantly favors their evolution to malignancies, manifesting primarily as colorectal adenocarcinomas though may also occur in other sections of the gastrointestinal tract, notably the duodenum. FAP polyps and malignancies seldom show early symptoms; family history is the most important diagnostic factor. Signs of FAP include specific dental anomalies and retinal changes that are apparent in childhood. Cancer experts recommend screening colonoscopy annually beginning in early adolescence, and every three to six months when polyp growth becomes pronounced.
Familial Adenomatous Polyposis (FAP) Treatment
Colonoscopy allows the gastroenterologist to remove large intestinal polyps and polyps showing dysplasia (cellular changes indicating that adenoma-to-adenocarcinoma transition is under way). Studies suggest some nonsteroidal antiinflammatory drugs (nsaids) may slow the growth of adenomas, reducing the number and size of the polyps. However, these medications do not alter the course of the disease, and surgery to remove the most heavily involved sections of intestine ultimately becomes the therapeutic solution.
Doctors often recommend prophylactic total bowel resection (removal of the colon and rectum) to eliminate the potential for colorectal cancer. Presently this is the only means to prevent FAP from developing into colorectal cancer. Advances in gene therapy show the greatest potential for less invasive and more effective treatments in the future. Participation in clinical research studies that are evaluating investigational treatments may present other treatment opportunities.
See also ADENOMA; CANCER PREVENTION; CANCER RISK FACTORS; CELL STRUCTURE AND FUNCTION; GENETIC DISORDERS; HEREDITARY NONPOLYPOSIS COLORECTAL CANCER (HNPCC); ILEOANAL RESERVOIR; ILEOSTOMY; INHERITANCE PATTERNS.
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