What are the causes and symptoms of familial polyposis?
FAP is caused by a portion of a gene that mutates or changes. The original cause of the mutation is unknown. Its exact role in FAP is not completely clear. Researchers theorize that the normal gene directs the manufacture of a protein which helps control cell growth. The mutated gene section in FAP generates an abnormal protein which does not perform its normal function. Cells grow out of control, causing the development of multiple, sometimes hundreds, of polyps. One or more of these eventually becomes cancerous. Many individuals develop polyps without displaying any symptoms. Others experience such gastrointestinal problems as diarrhea, constipation, abdominal cramps, blood in the stool, or weight loss. FAP patients may also develop nonmalignant tumors (desmoid tumors), and/or some bone and dental abnormalities. In addition, they may exhibit a “spot” on the retina of the eye (congenital hypertrophy of the retinal pigment epithelium, or CHRPE). Relatives of individuals with diagnosed
