Symptoms are uncommon until the adenomas are large and numerous causing hematochezia or anemia. Other non-specific complaints such as change in bowel habits, constipation, diarrhea and abdominal pain may occur.
Diagnosis is based on family history, clinical findings and large bowel endoscopy or full colonoscopy. Barium enema and virtual colonoscopy can also be used to suggest the diagnosis of FAP. The clinical diagnosis should be confirmed by genetic testing. Familial Adenomatous Polyposis is diagnosed in a patient with one of the following:
Treatment for the disorder depends on the genotype. Monitoring is mainly based on endoscopic surveillance to detect the onset of polyposis. Prophylactic colectomy in FAP is usually performed shortly after polyps are discovered.
Several surgical options exist: total abdominal colectomy with ileorectal anastomosis, total proctocolectomy with ileal pouch anal anastomosis, total proctocolectomy with end ileostomy and total proctocolectomy with continent ileostomy   .
Familial adenomatous polyposis is caused by different inheritance patterns and different genetic mutations. Mutations in the APC tumor suppressor gene cause classic familial adenomatous polyposis and attenuated familial adenomatous polyposis. Mutations in the MUTYH gene are associated with autosomal recessive familial adenomatous polyposis .
The reported incidence of familial adenomatous polyposis varies from 1 in 7,000 to 1 in 22,000 individuals worldwide. The mean age for the development of colon cancer in the untreated individual is 39 years. Males and females are equally affected .
Colorectal cancer and diffuse mesenteric fibromatosis are the two main causes of mortality. Diffuse mesenteric fibromatosis is reported in 4 to 32% of patients.
Mutations in the APC gene cause both classic and attenuated familial adenomatous polyposis. APC is a tumor suppressor protein that plays a central role in Wnt-1 signaling, in part by regulating the degradation of β-catenin, a protein that stimulates cell growth.
More than 300 different types of mutations are recognized today as the cause of FAP. Most of these mutations result in a truncated and nonfunctional protein. The most common mutation, occurring in about 10% of FAP patients, is a deletion mutation in codon 1309. The number of polyps and the time frame in which they become malignant depend on the location of the mutation in the gene. APC mutations have also been linked to other certain cancers such as pancreatic or gastric adenocarcinomas or thyroid cancer   .
Autosomal recessive FAP is characterized by a slightly increased risk of developing colorectal cancer and adenomas in both the upper and lower gastrointestinal tract and is caused by the inheritance of mutations in the base-excision-repair gene MUTYH. The phenotype of Autosomal recessive FAP is often indistinguishable from the other forms.
There are no guidelines for prevention of FAP.
Familial adenomatous polyposis (FAP) is an autosomal dominant inherited condition in which numerous adenomatous polyps form in the epithelium of the colon. These polyps transform into colon cancer if left untreated.
There are three variants known existed. First, the classic familial adenomatous polyposis itself. Second, “attenuated FAP” (originally called “hereditary flat adenoma syndrome”). These two conditions are caused by APC gene defects, a tumor suppressor gene that is located on band 5q21. Third, the “autosomal recessive FAP” (or “MYH-associated polyposis (MAP)”) which is caused by MUTYH gene defects. The classic familial adenomatous polyposis is the most common and most severe form .
The presence of extracolonic manifestations is variable and may include gastric and duodenal polyps, dental abnormalities, congenital hypertrophy of the retinal pigment epithelium (CHRPE), osteomas, benign cutaneous lesions, diffuse mesenteric fibromatosis, hepatoblastoma, and extracolonic cancers.
Familial adenomatous polyposis is a rare genetic condition that causes polyps to form in the intestines. If untreated, these polyps almost always turn into cancer, usually by age 40.
FAP affects approximately 1 in 10,000 people, men and women equally. The majority of cases are due to a mutation in the adenomatous polyposis coli (APC) gene. Most people with familial adenomatous polyposis need surgery to remove the colon with all its polyps to prevent cancer.