Familial polyposis of the colon causes widespread development of adenomas in the colon and rectum. The number of polyps can range from no detectable polyps at colonoscopy to more than 7,000 seen on resected specimens of bowel. The polyposis predominantly affects the distal colon.
Attenuated familial adenomatous polyposis (AFAP)
Attenuated familial adenomatous polyposis is characterised by fewer colonic polyps (100 or less) and a delayed onset of symptoms and complications. The colonic polyps tend to involve the proximal colon and spare the rectum.
- The true incidence of attenuated familial adenomatous polyposis is not known.
- There is a delay in onset of adenomatosis and bowel symptoms of 20-25 years, a delay in onset of colorectal cancer of 10-20 years and a delay in death from colorectal cancer of 15-20 years.
- Because of the tendency to affect the proximal colon, colonoscopy is preferred to sigmoidoscopy for surveillance, which should begin at the age of 20-25 years.
- There are often associated gastric and duodenal adenomas and so regular upper gastrointestinal endoscopy is also recommended.
Gardner's syndrome is characterised by colonic polyposis with osteomas and soft tissue tumours. Turcot's syndrome is the association of colonic polyposis and tumours of the central nervous system. In 1951 Gardner described the occurrence of familial adenomatous polyposis with the extra-colonic manifestations of desmoids, osteomas and epidermoid cysts.
- The incidence of familial polyposis of the colon is about 1 in 10,000 live births.
- Colonic polyps begin developing at a mean age of 15 years.
- Familial polyposis syndromes have autosomal dominant inheritance with almost complete penetrance but marked variation in expression. Mutations of the APC gene on chromosome 5 are thought to be responsible.
- The location of the mutation on the gene is thought to influence the nature of the extra-colonic manifestations.
- Adenomas usually begin to develop during the second decade of life.
- Unfortunately, it often presents with colorectal cancer.
- The median age at diagnosis is 40 years.
- Patients are often asymptomatic but may present with rectal bleeding, diarrhoea, abdominal pain and mucous discharge.
- Obstruction may cause constipation, vomiting and peritonitis.
- Dental abnormalities may cause jaw pain.
- Gastric polyps may cause epigastric pain or bleeding.
- Duodenal polyps may cause pain, bleeding or obstructive jaundice.
- Polyps in the ileum may cause obstruction.
- Thyroid carcinoma may present as a neck mass, pain, hoarseness and features of hypothyroidism or hyperthyroidism.
- Rectal polyps or masses.
- Other commonly associated features:
- Congenital hypertrophy of the retinal pigment epithelium (CHRPE) - evaluated by slit-lamp examination and indirect ophthalmoscopy - which can be a useful early clue as to whether the patient is a carrier of the APC gene.
- Dental problems - supernumerary teeth, odontomas, non-erupted teeth.
- Epidermoid cysts.
- Desmoid tumours or osteomas (skull, endosteal and exosteal osteomas).
- Thyroid masses.
- Carcinoembryonic antigen testing: raised levels may indicate colorectal carcinoma.
- LFTs to evaluate possible metastasis.
- Faecal occult blood.
- CT or MRI scan of the abdomen and pelvis.
- Dental X-rays, CXR and skull X-ray (for jaw lesions, osteomas, supernumerary teeth).
- Colonoscopy with biopsies: investigation of choice for diagnosis.
- Upper gastrointestinal endoscopy: for evaluation of gastric and duodenal polyps.
- Genetic testing: for the APC gene and its mutation. Prenatal testing is possible if a disease-causing mutation is identified in an affected family member.
Other hereditary polyposis syndromes include:
- Adenomatous polyposis syndromes - eg, Turcot's syndrome.
- Hamartomatous polyposis syndromes - eg, Peutz-Jeghers' syndrome, juvenile polyposis and Cowden's disease.
Peutz-Jeghers syndrome is an autosomal dominant disorder (with high penetrance) characterised by mucosal pigmentation of the lips and gums with multiple intestinal hamartomatous polyps.
- There is an associated marked increased risk of certain malignancies, especially gastro-oesophageal, small bowel, colorectal and pancreatic. There is also risk of ductal breast cancer, thyroid, lung, uterine, Sertoli cell testicular tumours or ovarian sex cord tumours.
- The estimate of the prevalence of Peutz-Jeghers syndrome is about 1 in 50,000.
- In up to two thirds of cases, mutations can be identified in the serine/threonine kinase gene STK11(LKB1) on chromosome 19 (19p13.3).
- Family history: asymptomatic but requesting investigation/counselling.
- Deeply pigmented lesions on the lips (cross the vermillion border) and buccal mucosa. These may also be present on the hands and feet (particularly the palms and the soles) and around the anus and genitalia. These lesions may be most prominent in infancy and fade after puberty.
- Repeated bouts of abdominal pain in a young patient (due to obstruction or intussusception).
- Unexplained intestinal bleeding in a young patient or iron-deficiency anaemia.
- May also present with rectal prolapse, precocious puberty, or with nasal, bronchial, biliary tract, uterine or bladder polyps.
- If Peutz-Jeghers syndrome is suspected on the basis of clinical criteria, the patient should be referred to a regional genetics centre for formal counselling and mutation analysis of the relevant gene.
- Surgical excision of lesions may be required:
- Endoscopic polypectomy for diagnosis and control of symptoms.
- Polypectomy using double balloon enteroscopy may prevent the need for repeated urgent operations and small bowel resection that leads to short bowel syndrome.
- Colorectal surveillance: large bowel surveillance is recommended two-yearly from the age of 25 years. The intervention should visualise the whole colon and so colonoscopy is the preferred mode of surveillance.
- Members of the family of an affected family where a causative gene has been identified should be referred for gene counselling and predictive gene testing. Where they test negative, there is no indication for their continued surveillance.
Diseases associated with familial polyposis coli
- Malignant tumours:
- Nasopharyngeal angiofibromas.
- Radiopaque jaw lesions.
- Supernumerary teeth.
- Lipomas, fibromas, epidermoid cysts.
- Desmoid tumours.
- Gastric adenomas.
- Duodenal, jejunal and ileal adenomas.
Screening by flexible sigmoidoscopy with biopsy of polyps for histological diagnosis confirms the condition and allows surgery before the age of 20. See also separate Screening for the Early Detection of Colorectal Cancer article.
- Aspirin and celecoxib may reduce recurrence of adenomas and the incidence of advanced adenomas in individuals with an increased risk of colorectal cancer.
- Treatment with sulindac, tamoxifen, or a combination of both, has been used for people with familial polyposis and desmoid tumours.
The types of surgery are:
- Proctocolectomy with ileostomy.
- Total colectomy with ileo-rectal anastomosis.
- Restorative proctocolectomy with ileo pouch anal anastomosis - the main surgical treatment for patients with familial adenomatous polyposis.
Complications secondary to polyps lining the colon include:
- Gastrointestinal haemorrhage.
- Gastrointestinal obstruction.
- Malignant change (if prophylactic colectomy is not performed). The risk of colorectal cancer increases with the number of polyps:
- The mean age of colon cancer diagnosis in untreated individuals is 35-40 years.
- Patients with more than 1,000 polyps have been proven to have 2.3 times the cancer risk compared to patients with fewer than 1,000 polyps.
- Colon cancer will develop in all affected individuals unless prophylactic colectomy is performed.
- After total colectomy with ileo-rectal anastomosis, the recurrence rate is 30% after 20 years and 45% after 30 years.
Screening family members by flexible sigmoidoscopy confirms or eliminates the diagnosis.
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