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Polymerase proofreading-associated polyposis (PPAP) | CION Cancer Clinics
Polymerase proofreading-associated polyposis, or PPAP, is a rare inherited condition that causes polyps in the bowel and raises the risk of bowel cancer. It comes from a fault in the proofreading part of the POLE or POLD1 gene, passed down from one parent. This page explains how it is recognised, how it differs from other polyposis conditions, and how it is usually managed. At CION Cancer Clinics, our oncologists explain what a gene result means for you and your family, and plan the checks that follow.
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Medically reviewed by Dr. Naresh GunduConsultant Medical Oncologist · MBBS, DNB (Internal Medicine), DM (Medical Oncology, AIIMS) · last reviewed September 2026, next review due September 2027
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The short answer
What is polymerase proofreading-associated polyposis?
It is an inherited condition in which the enzyme that copies DNA cannot check its own work properly. Copying errors build up in the cells lining the bowel, and polyps form. Some polyps can turn into cancer over time, which is why carriers are watched closely and polyps are removed early.
How it is passed down
PPAP is dominant. One faulty copy, from either parent, is enough to raise risk. Each child of a carrier has a one in two chance of inheriting it. The fault does not skip generations, though a carrier may never develop cancer.
How rare it is
PPAP is uncommon, even among people with many bowel polyps. It is far rarer than Lynch syndrome or classic familial adenomatous polyposis. Many doctors meet only a handful of families in a career, which is one reason it can be missed.
Rare does not mean unmanageable. Regular colonoscopy with removal of polyps is the main tool, and it works.The clues
What makes a doctor suspect PPAP?
No single sign proves it. These are the patterns that prompt a test.
Several polyps, found young
A colonoscopy finds more adenomas than expected for the person's age, often a modest number rather than hundreds. Adenomas are the type of polyp that can become cancer.
Bowel cancer at a young age
Bowel cancer in a teenager or young adult, where Lynch syndrome has been ruled out, is a strong reason to test the polymerase genes. The age at diagnosis matters more here than the number of relatives affected.
A tumour with a huge number of changes
Tumour testing sometimes shows an ultramutated pattern, with far more DNA changes than usual. That points to failed proofreading, although often the fault sits only inside the tumour.
Bowel and womb cancer in one family
Bowel and womb lining cancers across generations, with normal Lynch testing, can suggest a POLD1 or POLE fault.
Worth mentioning to the doctor
- Who had polyps, and how many
- Any cancer diagnosed young
- Earlier gene tests and their results
Not sure whether this applies to you?
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How is PPAP usually diagnosed?
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A colonoscopy or a cancer raises the question
Most families come to attention because one person had several polyps or an early bowel cancer.
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The common causes are checked
Doctors look for the more common causes, such as Lynch syndrome, APC and MUTYH, usually on one gene panel.
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POLE and POLD1 are read on the same panel
Many polyposis panels include both genes. The laboratory looks specifically at the proofreading region, because that is where harmful faults sit.
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The variant is classified carefully
Many variants in these genes are rare. Laboratories use dedicated rules, and sometimes tumour evidence, to decide whether one is harmful.
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The family is offered testing
Once a harmful variant is confirmed, blood relatives can be tested for that exact change, often before any polyps appear.
On your report
What do the words around PPAP mean?
- Adenoma
- A polyp made of gland cells that can slowly turn into cancer. It is the type removed during colonoscopy.
- Polyposis
- Having many polyps in the bowel. The number and type help point to a cause.
- Proofreading
- The copying enzyme's own check for errors, done as each new DNA letter is added.
- Autosomal dominant
- One faulty copy from either parent is enough. Sons and daughters are affected equally.
- Polypectomy
- Removing a polyp during colonoscopy, usually without any cut on the skin.
- Colectomy
- An operation to remove part or all of the large bowel. It is rarely the first step in PPAP.
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Side by side
How is PPAP different from classic FAP?
PPAP (POLE or POLD1)
Classic FAP (APC)
Tens of polyps, sometimes fewer
Often hundreds to thousands of polyps
Often controlled by regular colonoscopy
Usually needs bowel surgery in early adult life
Womb lining cancer risk, especially POLD1
No clear womb cancer risk
Duodenal polyps possible with POLE
Duodenal polyps are common
Rare and recently described
Well known and long studied
Commonly believed
What do people get wrong about PPAP?
"Polyposis always means the bowel has to be removed."
Not in PPAP. Most carriers are managed by removing polyps during regular colonoscopies. Surgery is considered only if polyps become too many to control, and that decision is made with a surgeon.
"Lynch testing was normal, so our family has no inherited cause."
Lynch syndrome is only one cause. PPAP, MUTYH and APC faults can all cause polyps and bowel cancer. A family with a strong pattern and a normal Lynch result may still need a wider test.
"PPAP only matters for the person who had polyps."
It is inherited. Each child of a carrier has a one in two chance of carrying it, and brothers and sisters may carry it too. Relatives can be tested before any polyps appear.
"An ultramutated tumour means an inherited fault."
Not by itself. Most ultramutated tumours carry a POLE change inside the tumour only. A blood test is needed to know whether the fault is in every cell and could affect relatives.
Being straight with you
What can this page not tell you?
It cannot tell you whether your family has PPAP. That takes a family history taken properly, the right gene test and a careful reading of the result. What your specific variant means is a question for the counsellor who ordered the test.
Where the evidence is thin
PPAP was first described just over a decade ago. Studies so far are small, and advice on which checks to add, and when, is still being refined. Your specialist will tell you which guidance they follow and why. Expect that advice to change as more families are studied, and ask how you will hear about it.
Who this does not apply to
Most people with a bowel polyp do not have PPAP. One or two polyps found later in life are common and rarely inherited. POLE findings in a tumour alone belong to treatment planning, covered under targeted therapy.
Questions we are asked
Common questions about PPAP
Is PPAP the same as FAP?
No. Both cause bowel polyps, but they come from different genes. FAP comes from APC and usually causes far more polyps. PPAP comes from POLE or POLD1, tends to cause fewer polyps, and adds risks in the womb lining or the duodenum.
Can PPAP be treated?
The gene fault cannot be corrected, but the risk it brings can be managed. Regular colonoscopy with removal of polyps is the main approach. Upper gut checks and, for women, attention to the womb lining may be added to the plan.
Will I need surgery?
Most carriers do not need bowel surgery if polyps can be kept under control at colonoscopy. Surgery becomes an option if polyps grow too many or a cancer is found. Preventive surgery for other organs is a separate discussion with a specialist.
When do checks start?
Guidelines differ, because the condition is rare. One expert group suggests starting bowel checks in the early teenage years, as cancers have occasionally been seen that young. Your specialist will set the starting point for your family.
Does PPAP affect fertility or pregnancy?
PPAP itself is not known to affect fertility. Women may be advised about womb lining checks, and couples can discuss family planning, including testing options, with a counsellor before a pregnancy.
Is PPAP seen in India?
It is rare everywhere, and very few Indian families have been reported. That probably reflects how rarely these genes have been tested here rather than a true difference. Wider panel testing is slowly changing this.
Does PPAP change treatment if cancer develops?
It can. Tumours from failed proofreading carry many DNA changes and may respond to immunotherapy. Surgeons may also plan the extent of bowel surgery differently. These choices are made by the treating team, based on the tumour itself.
Where do I start if I think my family has PPAP?
Write down who had polyps or cancer, in which organ and at roughly what age. Take that list and any colonoscopy reports to a genetic counsellor or gastroenterologist. Call the CION helpline if you are unsure who to see, and someone will point you to the right clinic.
Your Specialists
Meet CION's oncologists. Bring your family history or genetic report to them.
Our medical oncologists see people with a strong family history of cancer, arrange genetic counselling and testing where it fits, and plan the checks that follow.
Medical Oncologist
Dr. C. Raghavendra Reddy
MBBS(Gold Medal), DNB(General Medicine), DM(Medical Oncology)(Gold Medal)
Medical Oncologist
Dr. Bharati Devi Gorantla
MBBS, MD(General Medicine), DM(Medical Oncology)(Adyar,Chennai), ECMO, MRCP SCE(UK)
Medical Oncologist
Dr. Owais Mohammed
MBBS, MD (General Medicine), DrNB (Medical Oncology), ECMO, MRCP SCE (Medical Oncology) (UK)
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Sources
- Familial Cancer — The clinical features of polymerase proof-reading associated polyposis (PPAP) and recommendations for patient management
- NCBI MedGen — Polymerase proofreading-related adenomatous polyposis
- National Cancer Institute — Genetics of Colorectal Cancer (PDQ)
- Genome Medicine (PMC) — Recommendations for the classification of germline variants in the exonuclease domain of POLE and POLD1
This page is general information, not a prescription. Do not change or stop any treatment based on what you read here. If anything is worrying you, contact your own treating team — or call our helpline and we will help you reach the right specialist.
Keep reading
Related pages
POLE and POLD1 mutation: which cancers and what riskOrgan by organ, and where the evidence is thinSurveillance for POLE and POLD1 carriersWhich checks are offered, and whyTesting the family for POLE and POLD1Who should be tested once a fault is foundThe APC gene: what it doesThe gene behind classic FAP, for comparison
Talk to us
Has a colonoscopy found more polyps than expected?
Tell us what the report says and who else in the family has had polyps or cancer. We will help you work out whether a genetic referral makes sense. One helpline serves every CION centre.