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Health condition · Clinically reviewed

Familial adenomatous polyposis, genetics, surveillance and the case for prophylactic colectomy.

FAP is a rare but well-mapped inherited syndrome. With APC and MUTYH testing, a specialist registry and planned surgery, colorectal cancer is almost entirely preventable.

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Why trust this guide

  • 01

    Clinically reviewed

    Written by our editorial team and reviewed by a registered UK clinician before publication.

  • 02

    Sourced from guidance

    Checked against NICE, BSG, NHS England specialist commissioning and peer-reviewed sources you can see at the end.

  • 03

    Current for 2026

    Reflects UK specialist commissioning of FAP care, current APC and MUTYH genetic testing pathways and modern desmoid options.

Key facts

FAP at a glance.

The essentials, in plain English. What FAP is, how it is inherited, and how UK specialist centres manage it today.

  • What it is

    An autosomal dominant syndrome caused by germline APC mutations, producing more than 100 adenomatous polyps in the colon and rectum and a near-certain colorectal cancer risk if untreated.

  • How common

    Roughly 1 in 8,000 births. Around a quarter of cases arise from a new mutation with no family history.

  • Classic FAP

    Hundreds to thousands of colonic adenomas, typically appearing in the teenage years, with colorectal cancer almost universal by age 40 if the colon is not removed.

  • Attenuated FAP (AFAP)

    Fewer than 100 polyps, later onset in the 40s to 60s, often right-sided. Often linked to APC mutations at the 5-prime or 3-prime ends of the gene.

  • Gardner and Turcot

    Gardner syndrome combines FAP with osteomas, epidermoid cysts, desmoid tumours and CHRPE. Turcot syndrome links FAP with CNS tumours, particularly medulloblastoma.

  • MAP phenocopy

    Biallelic MUTYH mutations (MUTYH-associated polyposis) produce an AFAP-like picture and are inherited recessively rather than dominantly.

Why this guide matters

A registry-led plan, not a scramble.

FAP is rare and complex, but the pathway is well mapped. The three points below sit behind every decision on this page.

  • Genetics drives the whole plan

    Confirming an APC or biallelic MUTYH variant sets the diagnosis, guides surveillance intervals and enables cascade testing of relatives.

  • Surveillance is not optional

    Colonic, pouch or rectal surveillance plus upper GI endoscopy, thyroid ultrasound and hepatoblastoma screening in young children reduce cancer deaths.

  • Prophylactic colectomy is protective

    Removing the colon before cancer develops is the single most effective intervention. Timing and technique are individualised in specialist centres.

How the diagnosis is made

From family history to a clear surveillance plan.

The steps a UK clinical genetics service and specialist FAP centre will normally follow, in order, so you know what to expect.

  1. 01

    Assessing

    Family history and clinical suspicion

    A pedigree over three generations, plus questions about early bowel cancer, polyps, desmoid tumours, osteomas and CHRPE. Suspicion rises quickly with more than 10 to 20 cumulative adenomas.

  2. 02

    Assessing

    Specialist genetics referral

    FAP is managed through NHS specialist clinical genetics services. Referral is triggered by a clinical picture, a family history or an unexpectedly heavy polyp burden at colonoscopy.

  3. 03

    Assessing

    APC and MUTYH genetic testing

    Germline testing of APC (dominant) and MUTYH (recessive, biallelic) confirms the diagnosis and defines the variant for cascade testing of relatives.

  4. 04

    Confirming

    Cascade family testing

    Once a variant is identified, at-risk relatives are offered predictive testing through genetics. Children of an affected parent have a 50 per cent risk in classic FAP.

  5. 05

    Confirming

    Colonoscopy from age 10 to 12

    Baseline colonoscopy is commissioned from around age 10 to 12 in classic FAP, with annual or biennial surveillance thereafter until definitive surgery.

  6. 06

    Confirming

    Upper GI endoscopy from 25 to 30

    Forward and side-viewing endoscopy of the stomach and duodenum, with Spigelman staging of duodenal polyposis, at intervals set by stage.

  7. 07

    Preparing

    Extracolonic screening

    Annual thyroid ultrasound, AFP and abdominal ultrasound for hepatoblastoma in young children, dental review, and imaging for suspected desmoid disease.

Typical journey: from first referral to a settled surveillance and surgical plan within a few months.

Symptoms

What FAP actually looks like.

A colonic polyp burden, extracolonic features across the gut, thyroid, bones and skin, and the signals that mean it is time to escalate.

  • Hundreds of colonic polyps

    Carpeting adenomas across the colon and rectum, often visible from the teens in classic FAP.

  • Rectal bleeding and change of bowel habit

    Common presenting symptoms once polyps are numerous, though many people are picked up on cascade testing before symptoms.

  • Duodenal and gastric polyps

    Duodenal adenomas around the ampulla and fundic gland polyps in the stomach. Duodenal cancer is the second most common cause of death in FAP.

  • Desmoid tumours

    Locally aggressive fibromatoses, most often intra-abdominal after colectomy. See our guide to desmoid tumours.

  • Osteomas and dental changes

    Skull and jaw osteomas, unerupted or supernumerary teeth, and odontomas. Characteristic in Gardner syndrome.

  • Thyroid nodules and papillary cancer

    Around 2 to 3 per cent lifetime risk of papillary thyroid cancer, often multifocal and cribriform-morular in pattern.

  • Hepatoblastoma in young children

    A rare but recognised risk in the first five years of life, prompting AFP and abdominal ultrasound screening in affected families.

  • Red flag - obstruction or bleeding

    Bowel obstruction, heavy per-rectal bleeding, unexplained anaemia or a rapidly enlarging abdominal mass need urgent specialist review.

Treatment

How FAP is treated in the UK.

A specialist-commissioned MDT plan across colorectal surgery, upper GI endoscopy, endocrine surgery, oncology and clinical genetics.

  • Prophylactic colectomy

    The definitive treatment. Typically performed in late teens or early adulthood, timing individualised to polyp burden, dysplasia and life stage.

  • Restorative proctocolectomy with IPAA

    Total removal of the colon and rectum with an ileal pouch-anal anastomosis. Preferred when the rectum is heavily involved or dysplasia is present.

  • Total colectomy with IRA

    Total colectomy with ileorectal anastomosis, preserving the rectum. Requires lifelong rectal surveillance and can be an option when the rectum carries few polyps.

  • Proctocolectomy with end ileostomy

    Reserved for situations where a pouch is not feasible, for example advanced low rectal disease or desmoid disease compromising the mesentery.

  • Duodenal polyp management

    Endoscopic ampullectomy and polypectomy for early Spigelman stages, pancreas-preserving duodenectomy or pancreaticoduodenectomy for advanced stage IV disease.

  • Desmoid tumour therapy

    Active surveillance, sorafenib, nirogacestat, chemotherapy and highly selective surgery in specialist centres. See our desmoid tumours guide.

  • Chemoprevention with NSAIDs

    Sulindac and celecoxib reduce polyp number and size in selected patients. Used as an adjunct rather than a substitute for colectomy.

  • Thyroid and hepatoblastoma pathways

    Annual thyroid ultrasound with FNA for suspicious nodules, and AFP with abdominal ultrasound in young children to screen for hepatoblastoma.

What this guide is based on

The sources behind every claim on this page.

UK national guidance, specialist society consensus and NHS specialist commissioning standards, current at the time of last review.

Key references

Guidelines and standards we relied on.

A quiet reminder

This guide is for information, not medical advice.

Your clinical genetics team and specialist FAP centre know your family history and can tell you which parts apply to you. If in doubt, get seen.

  • NHS England. Specialised commissioning service specification for polyposis (FAP) registries and specialist centres.

  • British Society of Gastroenterology, ACPGBI and UKCGG. Guidelines for the management of hereditary colorectal cancer (2020).

  • NICE. Colorectal cancer (NG151) and molecular testing strategies for Lynch and polyposis syndromes.

  • European Society for Medical Oncology (ESMO). Clinical practice guidelines on familial risk-colorectal cancer.

  • St Mark's Hospital Polyposis Registry and Cambridge, Manchester and other UK FAP specialist centres - clinical protocols and patient information.

Red flags

When FAP needs urgent attention.

Much of FAP care runs on a planned surveillance rhythm. These are the situations that break that rhythm and need same-week specialist input.

  • Obstruction or perforation

    Sudden severe abdominal pain, distension or peritonism in someone with known FAP or a heavy polyp burden needs emergency assessment.

  • Heavy rectal bleeding or anaemia

    Unexplained iron-deficiency anaemia or persistent rectal bleeding warrants urgent endoscopy and specialist review.

  • Rapidly enlarging abdominal mass

    Especially after colectomy, this may represent a desmoid tumour and needs cross-sectional imaging in a specialist centre.

  • Advanced duodenal polyposis

    Spigelman stage IV disease, high-grade dysplasia or a duodenal mass carries a real cancer risk and should trigger surgical MDT review.

  • Thyroid nodule with suspicious features

    A hard, growing or FNA-suspicious nodule needs prompt endocrine surgical review, given the raised papillary thyroid cancer risk.

  • Neurological symptoms

    Headache, seizures or focal neurology in a young person with FAP should prompt urgent imaging to exclude a Turcot-pattern CNS tumour.

  • Symptoms in a young child

    A tender abdominal mass, jaundice or failure to thrive in an under-five in an FAP family should trigger urgent hepatoblastoma workup.

  • Missed or delayed surveillance

    Any gap of more than a year in colonic or duodenal surveillance in someone with known FAP should be corrected as a matter of urgency.

  • Pregnancy planning

    Family planning conversations should include preimplantation genetic testing, prenatal diagnosis and the timing of colectomy around pregnancy.

Living with it

A lifelong condition, with a well-mapped path.

Four things that make the biggest difference year to year - staying inside a specialist registry, keeping to surveillance, cascade testing your family and using the FAP support community.

A quiet reminder

Consistency beats intensity, every time.

A steady annual rhythm of scopes, ultrasound and clinic visits protects you far more than any single dramatic intervention.

  1. 01 Registry

    Stay connected to your specialist centre

    FAP care in the UK is commissioned through specialist polyposis registries. Keeping your registry contact up to date makes surveillance, surgery and cascade testing far easier.

  2. 02 Surveillance

    Never skip your annual scopes

    Colonic, pouch or rectal surveillance and upper GI endoscopy save lives in FAP. Diary them and rebook early if life gets in the way.

  3. 03 Family

    Cascade testing is part of care

    First-degree relatives should be offered predictive testing through clinical genetics. Early identification means surveillance rather than symptoms.

  4. 04 Support

    You are not on your own

    The FAP community, patient support groups and specialist nurses have decades of experience of colectomy, pouches, desmoids and family planning. Use them.

Frequently asked

Everything we get asked about FAP.

Quick answers on inheritance, genetic testing, prophylactic colectomy and extracolonic surveillance.

  • What is familial adenomatous polyposis?

    Familial adenomatous polyposis (FAP) is an autosomal dominant syndrome caused by germline mutations in the APC gene. It produces more than 100 adenomatous polyps in the colon and rectum and, if untreated, carries a near-certain risk of colorectal cancer, usually by age 40 in classic FAP.

  • How is FAP inherited and who should be tested?

    Classic FAP is autosomal dominant, so each child of an affected parent has a 50 per cent chance of inheriting the APC variant. MUTYH-associated polyposis is autosomal recessive and needs biallelic MUTYH mutations. First-degree relatives of a person with a confirmed variant should be offered predictive testing through NHS clinical genetics.

  • What is the difference between classic FAP, AFAP and Gardner syndrome?

    Classic FAP causes hundreds to thousands of polyps from the teenage years. Attenuated FAP (AFAP) causes fewer than 100 polyps, often right-sided and with later onset in the 40s to 60s. Gardner syndrome is FAP together with osteomas, epidermoid cysts, desmoid tumours, dental abnormalities and CHRPE. Turcot syndrome links FAP with CNS tumours such as medulloblastoma.

  • When is prophylactic colectomy usually recommended?

    For classic FAP, prophylactic colectomy is normally recommended in the late teens or early twenties, with exact timing decided by polyp burden, dysplasia, symptoms and personal circumstances. Options include restorative proctocolectomy with an ileal pouch (IPAA), total colectomy with ileorectal anastomosis, or proctocolectomy with an end ileostomy.

  • Do I still need surveillance after my colectomy?

    Yes. FAP is a lifelong condition. After colectomy you still need surveillance of any remaining rectum or of the ileal pouch, plus upper GI endoscopy for duodenal polyps, annual thyroid ultrasound and, in families with known risk, screening for desmoid disease and hepatoblastoma in young children.

  • What are the extracolonic risks in FAP and how are they screened?

    FAP carries additional risks including duodenal cancer, papillary thyroid cancer, desmoid tumours, hepatoblastoma in young children, adrenal adenomas and osteomas. Screening typically includes upper GI endoscopy with Spigelman staging from age 25 to 30, annual thyroid ultrasound, AFP and abdominal ultrasound in young children and imaging for suspected desmoid disease.

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