Clinical features

Age at clinical manifestation

Colorectal adenomas become detectable at endoscopic examination (sigmoi-doscopy) between the age of 10 and 20 years, increasing in number and size with age. The most important clinical feature of FAP is the almost invariable progression of one or more colorectal adenomas to cancer. The mean age of development of colorectal cancer is about 40 years, but the cancer risk is 1 to 6% already at

Fig. 6.52 Colectomy specimens from patients with familial adenomatous polyposis. A Hundreds of polyps of different size cover the entire mucosal surface. B Multiple adenomas in different stages of development. C Lateral view of polyps. D Numerous small early (sessile) adenomas.

Fig. 6.53 Tubulovillous adenoma in familial adenomatous polyposis.

the age of 20 to 25 years {835}, and col-orectal cancer has been reported even in children with FAP. Extracolonic manifestations such as epidermoid cysts, mandibular osteomas, desmoid tumours or congenital hypertrophy of the retinal pigment epithelium (CHRPE) may present in children and can serve as markers of FAP.

Symptoms and signs

In the early phase of FAP adenomas do not cause any symptoms. Specific symptoms due to colorectal adenomas are rectal bleeding and diarrhoea often accompanied by mucous discharge and abdominal pain. Symptoms appear gradually and may be easily overlooked; the mean age of appearance of symptoms was 33 years and the mean age of diagnosis 36 years in about 200 FAP patients who had no prophylactic screening arranged {216}.

Two thirds of patients diagnosed to have FAP on the basis of symptoms (propositi) already have colorectal cancer whereas in asymptomatic members of known FAP families cancer is very rare at the time of the detection of FAP provided that prophylactic endoscopic screening was arranged in good time, i.e. before the age of 20 years {836}.

Imaging and FAP screening

The appropriate screening method for diagnosing FAP is flexible sigmoi-doscopy, which should be arranged for all children of an affected FAP parent from the age of 10 to 15 years and continued at 1 to 2 year intervals up to the age of 40 years if adenomas are not detected. Endoscopies can be replaced by genetic testing for the specific APC mutation in those families where the mutation has been identified. A positive test is diagnostic for FAP and signifies the need for prophylactic colectomy or proctocolectomy when the colorectal adenomas become detectable, at the age of 20 to 25 years at the latest. If the operation is not performed immediately after the diagnosis of FAP, colonoscopy should be undertaken to evaluate the entire colon because large adenomas or cancer may reside beyond the reach of the flexible sigmoidoscope. Endoscopic evaluation of the upper gastrointestinal tract is recommended at the time of prophylactic colectomy or proctocolectomy, and should be repeated at 2 to 5 year intervals depending on the finding of adenomas in duodenal and gastric biopsies {688}. Double contrast barium enema and barium meal may be used to demonstrate polyps but are inferior to endoscopy because biopsies are required to provide histological evidence for a definite diagnosis of FAP

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