Adenomas, which are the precancerous type, do not develop at birth but may begin to appear in the rectum and colon from puberty onwards. In the beginning, there are frequently no warning signs to alert the patient to the development of polyps. Adenomas may not be diagnosed for ten years or longer. If left undiagnosed or untreated, one or more of the adenomas may become malignant by age 35-40 years. These figures are meant to represent guidelines rather than specific time limits since some individuals may be affected even after age 45 years.
Preventive surgery is required to preclude bowel cancer.
Early diagnosis, treatment, and follow-up are essential to cancer control. Therefore, it is estimated that about 300 to 600 individuals are affected in Hong Kong. Each child of a parent with FAP has a 50 per cent chance of inheriting the polyposis gene. Genes are the units of heredity in our body cells which pass on traits like eye colour, facial characteristics, and sometimes, diseases. If an affected parent has four children, this does not mean that two will have FAP and two will be unaffected.