saudigastro.com/patients/polyposis-syndromes-fap-lynch
Category
Chronic
Red flags
4
This article is educational and does not replace your doctor's advice. Seek urgent care for any red-flag symptoms.
What is it?
These are conditions passed down in families through changes (mutations) in certain genes. In familial adenomatous polyposis (FAP), a person develops many polyps in the large bowel, often starting in the teens or twenties; without treatment, cancer becomes almost certain over time. In Lynch syndrome there are usually fewer polyps, but the lifetime risk of bowel cancer, and also of womb (endometrial), ovarian, stomach and some other cancers, is higher than average, and cancers tend to occur at a younger age. Each child of an affected parent has about a one in two chance of inheriting the gene change.
How common is it?
These syndromes account for only a small share of all bowel cancers, but Lynch syndrome is the more common of the two. Many carriers do not know they have it, which is why family history matters so much.
Why does it happen?
FAP is usually caused by a change in a gene called APC. Lynch syndrome is caused by changes in genes that repair mistakes made when cells copy their DNA (mismatch repair genes). Because the repair system is faulty, errors build up and cancers can develop earlier. These gene changes are inherited; they are not caused by anything the person did, and they cannot be caught from someone else.
Symptoms
- Often none, especially in the early years, so family history and testing are important
- Rectal bleeding or blood in the stool
- A change in bowel habit, such as diarrhoea or constipation
- Belly pain or cramps
- Tiredness from iron-deficiency anaemia
- Weight loss
- In FAP, some people have other features such as growths in the duodenum or a harmless eye finding that doctors can look for
Red flags — seek urgent medical care
Rectal bleeding, especially with a change in bowel habit, in someone known to carry or at risk of the syndrome
Needs prompt specialist assessment; do not wait for the next routine colonoscopy. If bleeding is heavy or you feel faint, go to the emergency department.
Severe belly pain with vomiting and a swollen belly
May mean a blockage. Go to the emergency department.
Unplanned weight loss or new persistent tiredness
Should be assessed soon, as it could indicate a cancer or anaemia.
Abnormal vaginal bleeding after menopause or between periods in a woman with Lynch syndrome
Could be a sign of womb cancer, which is more likely in Lynch syndrome. See a doctor promptly.
How is it diagnosed?
Diagnosis begins with a detailed family history. Colonoscopy shows the number of polyps. Tumour tissue from a bowel cancer can be tested for features that suggest Lynch syndrome. Genetic testing, on a blood or saliva sample, can confirm the gene change. Testing is usually done with genetic counselling, which explains what results can and cannot tell you. Once a gene change is found in a family, relatives can be tested for that exact change, and those who do not carry it can usually return to routine screening. Your doctor decides who should be tested.
What the latest science says
Many centres now test bowel and womb cancer tissue routinely for features of Lynch syndrome, so more carriers are being identified. Surveillance is guided by the specific gene involved. For Lynch syndrome, regular colonoscopy has been shown to reduce cancer and deaths from it. Research is also looking at whether certain preventive medicines can help in selected carriers; this remains a decision for specialists.
Outlook — what to expect
These are lifelong conditions, but the outlook has improved a great deal. With regular surveillance in Lynch syndrome, and with timely bowel surgery in FAP, the risk of dying from bowel cancer can be greatly reduced. Knowing about the condition lets the whole family act early.
Treatment
Habits & Lifestyle
Lifestyle cannot remove the inherited risk, but it helps your general health and may modestly lower risk.
- Keep every surveillance colonoscopy and other scheduled checks, even when you feel well
- Do not smoke; smoking increases risk in carriers
- Limit alcohol and keep a healthy weight
- Share the diagnosis with relatives so they can consider genetic counselling
- Carry a note of your diagnosis and surveillance plan, and tell new doctors
Diet
Diet does not replace surveillance, but supports health.
- Eat plenty of vegetables, fruit, pulses and whole grains
- Limit red and processed meat
- After bowel surgery, a dietitian can help with fluids, salt and stool consistency
- Do not rely on supplements or special diets as a substitute for medical care
Medications
Medicines play a limited role, and any use is decided by a specialist.
- Aspirin has been studied for lowering cancer risk in Lynch syndrome; do not start it without specialist advice because of bleeding risk
- Some medicines have been tried to reduce polyps in FAP, but they do not replace surgery or colonoscopy
- Iron treatment may be needed for anaemia
- If bowel cancer develops, treatment (surgery, chemotherapy, immunotherapy) is chosen by the cancer team, and Lynch-related tumours sometimes respond well to immunotherapy
Procedures & Surgery
Regular scoping and, in some people, preventive surgery are the mainstays.
- Colonoscopy at regular, often short, intervals to find and remove polyps; in Lynch syndrome this usually starts in the twenties or thirties, as advised by your specialist
- In FAP, surgery to remove the colon (and sometimes the rectum) is usually advised at a time chosen by the specialist team, because polyps are too many to remove
- Upper endoscopy to check the stomach and duodenum is used in selected patients
- Women with Lynch syndrome may be offered womb and ovary checks, and preventive surgery may be discussed after childbearing is complete
Living with the condition
- Receiving this diagnosis can be a shock, and it affects the whole family. Genetic counsellors and support groups can help with the emotional side and with family planning decisions.
- Regular surveillance works best when it is a lifelong routine.
In the Saudi context
Because family marriage is common in some communities, and families are often large, tracing and testing relatives can be especially valuable. Genetic counselling services can help families decide who to test.
Questions to ask your doctor
Save this list or print it before your appointment — doctors appreciate prepared patients.
- Which gene change do I or my family have, and what does it mean for cancer risk?
- How often and from what age do I need colonoscopy or other checks?
- Do I need surgery, and when?
- Which relatives should be tested, and at what age should children be tested?
- Is aspirin or any other preventive medicine suitable for me?
- What should I consider for pregnancy and family planning?
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Status: Approved for publication by SGA; individual clinician review is ongoing · Published 24/04/2026
For general education only; it does not replace your doctor’s advice. Individual clinician review of this guide is ongoing. SGA clinician? Review this guide