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Juvenile polyposis syndrome
Juvenile polyposis syndrome (JPS) is a rare genetic disorder that increases the risk of developing numerous non-cancerous growths, called juvenile polyps, throughout the digestive system. Individuals with JPS have an elevated risk of bowel cancer and other cancers.
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Overview
Juvenile polyposis syndrome (JPS) is a rare inherited disorder that leads to the formation of benign (non-cancerous) growths, known as juvenile polyps, primarily in the large bowel (colon and rectum). These polyps can also occur in other parts of the digestive system, such as the stomach and small intestine [PMID:32578508]. While the polyps themselves are not cancerous, they carry a risk of transforming into malignant (cancerous) tumours over time. JPS is typically diagnosed in childhood or adolescence, though symptoms can appear at any age.
JPS is a genetically inherited condition, meaning it is passed down through families. It is part of a group of conditions known as hamartomatous polyposis syndromes, which are characterised by the presence of hamartomas - disorganised but benign tissue growths. Recognising the signs of JPS and managing the condition proactively is important for reducing cancer risks and improving health outcomes.
The estimated prevalence of JPS is around 1 in 100,000 people, making it a rare condition [PMID:17963288]. Due to its rarity, diagnosis can sometimes be delayed. However, advancements in genetic testing have improved the ability to identify individuals and families at risk, allowing for earlier surveillance and intervention strategies.
Symptoms & clinical features
The clinical presentation of juvenile polyposis syndrome can vary widely among affected individuals, even within the same family. Symptoms often depend on the number, size, and location of the polyps within the gastrointestinal tract. The most common symptoms are related to the bowel and often appear during childhood.
Common symptoms can include rectal bleeding, which may be visible in stools, and abdominal pain. Some individuals might experience chronic diarrhoea or constipation. Anaemia can develop due to persistent, subtle blood loss from the polyps, leading to symptoms like fatigue and paleness. In some cases, a polyp may protrude from the anus. Intussusception, where one part of the intestine slides into an adjacent part, is a less common but serious complication that can cause sudden, severe abdominal pain and vomiting. Occasionally, individuals may experience protein-losing enteropathy, which results in low protein levels in the blood and can cause swelling (oedema).
While most polyps are found in the large bowel, their presence in the stomach can lead to symptoms such as nausea, vomiting, or stomach pain. Polyps in the small intestine are less common but can also cause similar digestive issues. The presence of multiple polyps throughout the digestive system underscores the importance of a comprehensive approach to diagnosis and management.
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Affected organs
Juvenile polyposis syndrome primarily affects the gastrointestinal tract, which includes the oesophagus, stomach, small intestine, and large bowel (colon and rectum). The characteristic feature of JPS is the development of juvenile polyps in these organs.
The large bowel is the most commonly affected organ, where numerous polyps can develop. These polyps are typically benign but have a risk of becoming cancerous over time. The stomach can also be affected, with polyps occurring less frequently than in the large bowel. When stomach polyps are present, they can sometimes lead to symptoms such as discomfort or bleeding. Polyps in the small intestine are rarer but can also contribute to digestive issues and bleeding. In some cases, polyps may also be found in the oesophagus.
Beyond the digestive system, individuals with JPS may, in rare instances, have other features. For example, some may present with features such as brain abnormalities, heart defects, or cleft lip/palate, though these are not typical for most individuals with JPS. The primary concern and focus of clinical management remain the gastrointestinal manifestations and associated cancer risks.
Risks & severity
The severity of juvenile polyposis syndrome can vary significantly, ranging from individuals with a few polyps and relatively mild symptoms to those with numerous polyps and more serious complications. The main concern with JPS is the increased lifetime risk of developing gastrointestinal cancers, particularly colorectal cancer. Estimates suggest that individuals with JPS have a lifetime risk of colorectal cancer ranging from 9% to 50% [PMID:17963288]. There is also an increased risk of stomach cancer, with estimates around 21% [PMID:17963288]. Less commonly, there may be an elevated risk of cancers in the small intestine and pancreas.
The age of onset for polyps can range from infancy through to adulthood, but they are most frequently identified during childhood or adolescence. Cancer development in individuals with JPS tends to occur at an earlier age compared to the general population, often in their 30s or 40s. The number of polyps present can influence the risk of cancer; individuals with more polyps generally face a higher risk. Factors such as the specific gene involved and family history of cancer can also contribute to the overall risk profile and severity of the condition.
Regular surveillance and proactive management are crucial for individuals with JPS to monitor polyp development and detect any cancerous changes early. This often involves frequent endoscopic examinations, starting in childhood or adolescence, to identify and remove polyps before they can become malignant. The goal of management is to mitigate the risks associated with JPS and improve long-term health outcomes.
Genetic causes
Juvenile polyposis syndrome is caused by pathogenic variants (changes) in certain genes. The two genes most commonly implicated in JPS are *BMPR1A* and *SMAD4*. These genes play vital roles in the transforming growth factor beta (TGF-β) signalling pathway, which is essential for regulating cell growth, differentiation, and programmed cell death. When these genes do not function correctly, it can lead to the uncontrolled cell proliferation that results in polyp formation.
The *BMPR1A* gene provides instructions for making a protein called bone morphogenetic protein receptor type 1A. This protein is a receptor found on the surface of cells and is involved in transmitting signals from outside the cell to the inside. These signals are crucial for controlling cell division and development. Pathogenic variants in *BMPR1A* disrupt this signalling, contributing to the development of juvenile polyps.
Similarly, the *SMAD4* gene provides instructions for making a protein that acts as a central mediator in the TGF-β signalling pathway. This protein helps relay signals from the cell surface receptors to the cell nucleus, where they influence gene activity. When *SMAD4* is altered, the cellular communication pathway is disrupted, leading to abnormal cell growth and an increased risk of polyp formation and cancer [PMID:17963288]. In some cases, individuals with JPS may not have an identified pathogenic variant in *BMPR1A* or *SMAD4*, suggesting that other genes may also be involved in the condition.
- BMPR1A bone morphogenetic protein receptor type 1AThe BMPR1A gene provides instructions for a protein critical in cell growth, division, and differentiation, primarily through the transforming growth factor beta (TGF-β) signalling pathway.
- SMAD4 SMAD family member 4The SMAD4 gene provides instructions for a protein crucial in cellular signalling, regulating cell growth and division, and acting as a tumour suppressor.
Inheritance pattern
Juvenile polyposis syndrome is inherited in an autosomal dominant pattern. This means that a person only needs to inherit one copy of an altered gene (*BMPR1A* or *SMAD4*) from either parent to develop the condition. If a parent has JPS, there is a 50% chance with each pregnancy that their child will inherit the pathogenic variant and therefore develop the syndrome.
In about 50% of JPS cases, the condition arises from a 'de novo' (new) pathogenic variant, meaning the change in the gene occurs for the first time in that individual and was not inherited from either parent. In such instances, neither parent carries the pathogenic variant, but the affected individual can still pass it on to their children [PMID:32578508].
Family members of someone diagnosed with JPS, particularly first-degree relatives (parents, siblings, children), may be offered genetic counselling. This can help them understand their own risk of carrying the pathogenic variant, the chances of passing it on, and the availability of genetic testing. Identifying at-risk family members is crucial for implementing early surveillance and management strategies, even if they currently show no symptoms.
Each child has a 50% chance of inheriting the pathogenic variant, regardless of sex.
Diagnosis & testing
The diagnosis of juvenile polyposis syndrome typically begins with a clinical suspicion based on symptoms or a family history of the condition. Clinical criteria for diagnosing JPS include having more than five juvenile polyps in the large bowel, juvenile polyps throughout the gastrointestinal tract, or any number of juvenile polyps with a family history of JPS [PMID:32578508]. Endoscopic procedures, such as colonoscopy and gastroscopy, are often performed to visualise and remove polyps, and tissue samples (biopsies) are taken for histological examination to confirm they are juvenile polyps.
Once a clinical diagnosis is suspected, genetic testing is usually offered to confirm JPS and identify the specific pathogenic variant responsible. This testing often involves looking for changes in the *BMPR1A* and *SMAD4* genes. Genetic testing can be performed on a blood sample and helps to confirm the diagnosis, guide surveillance strategies, and enable cascade testing for at-risk family members. In the UK, such testing typically falls under the NHS Genomic Medicine Service (GMS) and may be accessed via specific R-codes, such as R216 Inherited polyposis. Referral to a clinical genetics service is usually required to access these tests and receive appropriate genetic counselling.
Management & lifestyle
Managing juvenile polyposis syndrome focuses on regular surveillance to detect and remove polyps, thereby reducing the risk of cancer. The management plan is highly individualised, depending on the specific gene involved, the number and location of polyps, and family history. Regular endoscopic examinations, including colonoscopy and gastroscopy, are standard practice. These procedures allow clinicians to monitor the gastrointestinal tract, remove any new or growing polyps, and take biopsies to check for any signs of cancerous changes. The frequency of these surveillance procedures is tailored to the individual's risk profile, often starting in childhood or adolescence.
If numerous polyps are present, or if there is a significant risk of cancer, surgical interventions may be considered. This could include procedures such as a colectomy (removal of part or all of the large bowel) to prevent cancer development, especially if polyps cannot be effectively managed endoscopically or if high-grade dysplasia (pre-cancerous changes) is detected. Clinical genetics services and multidisciplinary teams, including gastroenterologists and surgeons, work together to develop a comprehensive management strategy.
There are no specific medications to prevent polyp formation in JPS, but supportive care for symptoms like anaemia or abdominal pain may be provided. Lifestyle considerations generally include maintaining a healthy diet and discussing any specific dietary advice with a healthcare professional, though these do not directly prevent polyps. Genetic counselling is an integral part of management, providing information and support to affected individuals and their families, and helping them navigate the implications of JPS.
UK care pathway
In the UK, individuals suspected of having juvenile polyposis syndrome are typically referred to a clinical genetics service. This referral may come from their GP or a specialist such as a gastroenterologist. The clinical genetics team will assess the individual's personal and family history and may offer genetic testing to identify the underlying genetic cause, often using the NHS Genomic Medicine Service (GMS). Genetic tests for inherited polyposis syndromes, including JPS, are available through specific R-codes, such as R216 Inherited polyposis.
Following a confirmed genetic diagnosis, individuals and their families will receive genetic counselling to understand the inheritance pattern, recurrence risks, and implications for other family members. A personalised surveillance plan will then be developed by a multidisciplinary team, which usually includes a gastroenterologist, surgeon, and geneticist. This plan typically involves regular endoscopic examinations to monitor for and remove polyps. Ongoing support and information are provided through these specialist services.
Frequently asked questions
What is the difference between a 'juvenile polyp' and other polyps?
Juvenile polyps are a specific type of benign growth, often found in the large bowel, characterised by their smooth, rounded appearance and abundance of inflammatory cells. Unlike some other polyp types, they are not typically considered precancerous from their initial formation, but their presence in large numbers, as in Juvenile Polyposis Syndrome, significantly increases cancer risk over time.
If I have JPS, will my children definitely inherit it?
Juvenile Polyposis Syndrome is inherited in an autosomal dominant pattern. This means if you have JPS, there is a 50% chance with each child you have that they will inherit the pathogenic gene variant and also develop the condition. Genetic counselling can provide more personalised information about your specific risks.
How often will I need to have colonoscopies if I have JPS?
The frequency of colonoscopies and other endoscopic surveillance procedures is determined by your clinical team. It depends on several factors, including the specific gene variant, the number and size of polyps found, your age, and your family history. Surveillance often begins in childhood or adolescence and continues regularly throughout life.
Can JPS polyps become cancerous?
While juvenile polyps themselves are initially benign, in individuals with Juvenile Polyposis Syndrome, there is a significantly increased lifetime risk that these polyps can develop into cancer, particularly colorectal cancer. Regular surveillance and polyp removal are crucial to detect and prevent cancerous changes.
Is there a cure for Juvenile Polyposis Syndrome?
There is currently no cure for the underlying genetic cause of Juvenile Polyposis Syndrome. However, the condition is manageable through regular screening, endoscopic removal of polyps, and sometimes surgical interventions to reduce the risk of cancer. This proactive management helps individuals live full and healthy lives.
References
- Adam MP, Bick S, Mirzaa GM. Juvenile Polyposis Syndrome. 1993. PMID: 20301642
- Brosens LA, Langeveld D, van Hattem WA. Juvenile polyposis syndrome. World journal of gastroenterology. 2011. PMID: 22171123
- McCarthy AJ, Chetty R. Smad4/DPC4. Journal of clinical pathology. 2018. PMID: 29720405
- Syngal S, Brand RE, Church JM. ACG clinical guideline: Genetic testing and management of hereditary gastrointestinal cancer syndromes. The American journal of gastroenterology. 2015. PMID: 25645574
- Rebuzzi F, Ulivi P, Tedaldi G. Genetic Predisposition to Colorectal Cancer: How Many and Which Genes to Test? International journal of molecular sciences. 2023. PMID: 36768460
- Hussain T, Church JM. Juvenile polyposis syndrome. Clinical case reports. 2020. PMID: 31998494
- Cichy W, Klincewicz B, Plawski A. Juvenile polyposis syndrome. Archives of medical science : AMS. 2014. PMID: 25097590
- Dal Buono A, Gaiani F, Poliani L. Juvenile polyposis syndrome: An overview. Best practice & research. Clinical gastroenterology. 2022. PMID: 35988962