requires both parents to be 'carriers' to manifest the condition. In some cases FAP can manifest higher in the colon than usual (for example, the ascending colon, or proximal to the splenic flexure, or in the stomach or duodenum) where they show no symptoms until cancer is present and greatly advanced. APC mutations have been linked to certain other cancers such as thyroid cancer. As the mutation causing FAP is autosomal dominant, it can be inherited directly from either parent to a child. A genetic blood test of the APC gene exists that can determine whether it is present, and therefore can predict the possibility of FAP. Individuals at risk (due to family links or genetic testing) are usually offered routine monitoring of the intestinal tract every 1–3 years for life, from puberty for FAP and early adulthood for attenuated forms. Colon resection surgery is recommended if numerous colon polyps are found due to high risk of early death from colon cancer. International polyposis registries exist that track known cases of FAP or APC gene defects, for research and clinical purposes. Mutation of APC also occurs commonly in incident cases of colorectal carcinoma, emphasizing its importance in this form of cancer. Signs and symptoms From early adolescence, patients with this condition gradually (and much of the time asymptomatically) develop hundreds to thousands of colorectal polyps (and sometimes polyps elsewhere)—small abnormalities at the surface of the intestinal tract, especially in the large intestine including the colon or rectum. These may bleed, leading to blood in the stool. If the blood is not visible, it is still possible for the patient to develop anemia due to gradually developing iron deficiency. If malignancy develops, this may present with weight loss, altered bowel habit, or even metastasis to the liver or elsewhere. FAP can also develop 'silently' in some individuals, giving few or no signs until it has developed into advanced colorectal cancer. Because familial polyposis develops very gradually over years, and can also manifest in an 'attenuated' form even more gradually, polyps resulting from FAP can lead to cancer developing at any point from adolescence to old age. Depending on the nature of the defect in the APC gene, and whether it is the full or attenuated form, familial polyposis may manifest as polyps in colon or in the duodenal tract, or in any combination of these. Therefore, an absence of polyps in,