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PubMed This is a summary of 17 peer-reviewed journal articles Updated
Gastroenterology

Decoding the DNA: Genetics and Subtypes

At a Glance

Juvenile Polyposis Syndrome (JPS) is primarily driven by mutations in the SMAD4 or BMPR1A genes. Knowing your specific mutation is critical, as it determines whether you need targeted screening for stomach cancer, colon polyps, or hidden blood vessel issues like HHT.

While the symptoms of Juvenile Polyposis Syndrome (JPS) may look similar from the outside, the “instruction manual” (DNA) behind them can vary significantly. About 40% to 50% of people with JPS have a mutation in one of two specific genes: SMAD4 or BMPR1A [1][2]. Identifying which gene is involved—or if a larger piece of DNA is missing—is critical because it tells your doctors exactly where to look for future problems.

The Two Main Subtypes: SMAD4 vs. BMPR1A

The “type” of JPS you or your child has is determined by which gene is affected.

  • SMAD4 Mutation: This version is often considered more aggressive. Patients with SMAD4 changes have a significantly higher risk of developing polyps in the stomach, which can lead to a higher risk of gastric (stomach) cancer over time [3][4].
    • The HHT Connection: This mutation also causes a combined syndrome where JPS overlaps with Hereditary Hemorrhagic Telangiectasia (HHT) [5]. This means the body may form abnormal connections between arteries and veins (Arteriovenous Malformations or AVMs) in the lungs, brain, or liver, which require their own specialized screening [6][7].
  • BMPR1A Mutation: This type primarily affects the colon and rectum [8]. While the risk for colon polyps remains high, the risk for stomach involvement is typically lower than in the SMAD4 type [9][3].

Juvenile Polyposis of Infancy (JPI)

The most severe form of JPS occurs in very young infants and is usually caused by a 10q23 microdeletion [10].

  • A “Two-for-One” Loss: In JPI, a small piece of chromosome 10 is missing. This missing piece includes both the BMPR1A gene and a neighboring gene called PTEN [10][11].
  • The Result: The loss of both genes at once causes an extremely rapid and severe growth of polyps throughout the entire digestive tract within the first months of life. This often leads to the severe protein loss and malnutrition [12][11].

Why Genetic Testing Is Critical

Genetic testing is not just about giving the condition a name; it is a vital tool for personalized care.

  1. Tailored Surveillance: If you have a SMAD4 mutation, your doctors will start checking your stomach much earlier and more frequently than they would for someone with BMPR1A [4][13].
  2. Screening Beyond the Gut: Only genetic testing can confirm if you need to be screened for the hidden vascular (blood vessel) risks associated with HHT [5].
  3. Cascade Testing for the Family: Because JPS has a 50% chance of being passed from parent to child, once a mutation is found in one person, other family members can be tested for that specific change [14]. This allows relatives to either be cleared of the risk or start life-saving screening before they ever develop a single symptom [15].

Family Planning and Reproductive Options

Learning about the 50% inheritance risk can be incredibly stressful for patients of childbearing age. You do not have to assume that having a family is impossible or guaranteed to pass on the condition.

You should ask for a referral to a reproductive genetic counselor. They can discuss medical options to protect future generations, such as In Vitro Fertilization (IVF) with Preimplantation Genetic Testing (PGT). This advanced process allows doctors to test embryos for the specific SMAD4 or BMPR1A mutation and only implant embryos that do not carry the JPS gene.

Even if your genetic test comes back “negative” (meaning no mutation was found), you can still have JPS based on your symptoms. In about 50% of cases, the genetic cause is still unknown to science [16][17]. In these instances, doctors will provide care based on your family history and how many polyps they find.

Common questions in this guide

What are the main genetic mutations that cause Juvenile Polyposis Syndrome?
The two most common genetic causes of JPS are mutations in the SMAD4 or BMPR1A genes. Together, these account for about 40% to 50% of all cases, while the other 50% currently have no known genetic cause.
How does a SMAD4 mutation affect my JPS screening and care?
A SMAD4 mutation increases the risk of stomach polyps and gastric cancer, so doctors will screen your stomach earlier and more often. It is also linked to a condition called HHT, which requires special scans to check for abnormal blood vessels in the lungs, brain, or liver.
What is Juvenile Polyposis of Infancy (JPI)?
JPI is the most severe form of the syndrome, caused by a missing piece of DNA that includes both the BMPR1A and PTEN genes. It causes rapid, widespread polyp growth in the digestive tract during the first months of life, leading to severe protein loss and malnutrition.
Can I still have JPS if my genetic test comes back negative?
Yes. In about half of all JPS cases, the specific genetic cause is still unknown to science. If your test is negative, doctors will still diagnose and treat you based on your clinical symptoms, how many polyps they find, and your family history.
Can Juvenile Polyposis Syndrome be passed down to my children?
Yes, JPS has a 50% chance of being passed from parent to child. However, if your specific mutation is known, working with a reproductive genetic counselor can provide options like IVF with preimplantation genetic testing to avoid passing the condition to future generations.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Which genetic mutation was found in our family (SMAD4, BMPR1A, or a 10q23 deletion), and how does that change our cancer screening schedule?
  2. 2.Since SMAD4 is linked to HHT, which specific tests (like a brain MRI or 'bubble echo' for the lungs) do we need to check for vascular malformations?
  3. 3.If we haven't found a mutation yet, should we consider more advanced testing like chromosomal microarray or whole exome sequencing?
  4. 4.When should my other children or family members undergo genetic testing?
  5. 5.Can you refer us to a reproductive genetic counselor to discuss family planning options?

Questions For You

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References

References (17)
  1. 1

    Disease expression in juvenile polyposis syndrome: a retrospective survey on a cohort of 221 European patients and comparison with a literature-derived cohort of 473 SMAD4/BMPR1A pathogenic variant carriers.

    Blatter R, Tschupp B, Aretz S, et al.

    Genetics in medicine : official journal of the American College of Medical Genetics 2020; (22(9)):1524-1532 doi:10.1038/s41436-020-0826-1.

    PMID: 32398773
  2. 2

    Patients with 10q22.3q23.1 recurrent deletion syndrome are at risk for juvenile polyposis.

    Lecoquierre F, Cassinari K, Chambon P, et al.

    European journal of medical genetics 2020; (63(4)):103773 doi:10.1016/j.ejmg.2019.103773.

    PMID: 31561016
  3. 3

    Occurrence of gastric cancer in patients with juvenile polyposis syndrome: a systematic review and meta-analysis.

    Singh AD, Gupta A, Mehta N, et al.

    Gastrointestinal endoscopy 2023; (97(3)):407-414.e1 doi:10.1016/j.gie.2022.10.026.

    PMID: 36265529
  4. 4

    SMAD4 variants and its genotype-phenotype correlations to juvenile polyposis syndrome.

    Cao K, Plazzer JP, Macrae F

    Hereditary cancer in clinical practice 2023; (21(1)):27 doi:10.1186/s13053-023-00267-z.

    PMID: 38066625
  5. 5

    Case report of juvenile polyposis/hereditary hemorrhagic telangiectasia syndrome: first report in Korea with a novel mutation in the SMAD4 gene.

    Kang B, Hwang SK, Choi S, et al.

    Translational pediatrics 2021; (10(5)):1369-1376 doi:10.21037/tp-21-12.

    PMID: 34189096
  6. 6

    Juvenile polyposis syndrome-hereditary hemorrhagic telangiectasia associated with a SMAD4 mutation in a girl.

    Hashimoto Y, Yokoyama K, Kumagai H, et al.

    Clinical journal of gastroenterology 2020; (13(6)):1096-1101 doi:10.1007/s12328-020-01238-w.

    PMID: 32944796
  7. 7

    JP-HHT phenotype in Danish patients with SMAD4 mutations.

    Jelsig AM, Tørring PM, Kjeldsen AD, et al.

    Clinical genetics 2016; (90(1)):55-62 doi:10.1111/cge.12693.

    PMID: 26572829
  8. 8

    Deciphering the clinical spectrum of gastric disease in patients with juvenile polyposis syndrome.

    Muller M, Baldysiak E, Benech N, et al.

    Gastrointestinal endoscopy 2024; (100(5)):867-877 doi:10.1016/j.gie.2024.05.015.

    PMID: 38777277
  9. 9

    Genotype-phenotype correlation of BMPR1a disease causing variants in juvenile polyposis syndrome.

    Papadopulos ME, Plazzer JP, Macrae FA

    Hereditary cancer in clinical practice 2023; (21(1)):12 doi:10.1186/s13053-023-00255-3.

    PMID: 37400896
  10. 10

    mTOR inhibitors reduce enteropathy, intestinal bleeding and colectomy rate in patients with juvenile polyposis of infancy with PTEN-BMPR1A deletion.

    Taylor H, Yerlioglu D, Phen C, et al.

    Human molecular genetics 2021; (30(14)):1273-1282 doi:10.1093/hmg/ddab094.

    PMID: 33822054
  11. 11

    Successful Treatment of Juvenile Polyposis of Infancy With Sirolimus.

    Busoni VB, Orsi M, Lobos PA, et al.

    Pediatrics 2019; (144(2)) doi:10.1542/peds.2018-2922.

    PMID: 31366686
  12. 12

    Polygenic Infantile Juvenile Polyposis Syndrome Managed With Sirolimus and Endoscopic Polypectomy.

    Bell LD, Bernat JA, Rahhal R

    Gastroenterology research 2022; (15(1)):33-38 doi:10.14740/gr1480.

    PMID: 35369680
  13. 13

    Malignant tumors associated with juvenile polyposis syndrome in Japan.

    Ishida H, Ishibashi K, Iwama T

    Surgery today 2018; (48(3)):253-263 doi:10.1007/s00595-017-1538-2.

    PMID: 28550623
  14. 14

    Familial juvenile polyposis syndrome with a de novo germline missense variant in BMPR1A gene: a case report.

    Liu Q, Liu M, Liu T, Yu Y

    BMC medical genetics 2020; (21(1)):196 doi:10.1186/s12881-020-01135-6.

    PMID: 33032550
  15. 15

    Collaborative Group of the Americas on Inherited Gastrointestinal Cancer Position statement on multigene panel testing for patients with colorectal cancer and/or polyposis.

    Heald B, Hampel H, Church J, et al.

    Familial cancer 2020; (19(3)):223-239 doi:10.1007/s10689-020-00170-9.

    PMID: 32172433
  16. 16

    Phenotypic Differences in Juvenile Polyposis Syndrome With or Without a Disease-causing SMAD4/BMPR1A Variant.

    MacFarland SP, Ebrahimzadeh JE, Zelley K, et al.

    Cancer prevention research (Philadelphia, Pa.) 2021; (14(2)):215-222 doi:10.1158/1940-6207.CAPR-20-0348.

    PMID: 33097490
  17. 17

    Parents' perspectives of non-informative germline genetic testing in children with Juvenile Polyposis Syndrome.

    Rud K, Smith-Simmer K, Weiss J, Garcia K

    Journal of genetic counseling 2025; (34(6)):e70140 doi:10.1002/jgc4.70140.

    PMID: 41250152

This information about JPS genetics is for educational purposes only. Always consult a genetic counselor or medical professional for personalized genetic testing, diagnosis, and family planning advice.

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