Familial Juvenile Polyposis

Familial juvenile polyposis, also known as juvenile polyposis syndrome, is an autosomal dominant condition characterized by the growth of hyperplastic, hamartomatous polyps in the colon. Polyposis syndromes are a group of inherited or acquired conditions characterized by the growth of polyps in the GI tract, and are associated with other extracolonic features. These syndromes are caused by mutations in specific genes associated with tumor suppression or cell cycle regulation. Familial juvenile polyposis is commonly associated with mutations in the SMAD4 (chromosome 18q) and BMPR1A (chromosome 10q) genes. Diagnosis is made by visualizing 5 or more polyps on colonoscopy, or any number plus a positive family history. Management is surgical in order to reduce the likelihood of GI bleeding and obstruction.

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Overview

Definition

Familial juvenile polyposis is an autosomal dominant condition characterized by the growth of hyperplastic, hamartomatous polyps in the colon.

Epidemiology

  • Most common type of hamartomatous polyp
  • Most common in children between the ages of 5 and 15 years
  • Approximately 50% of patients have a family history of the condition.
  • Increased risk of colorectal cancer (CRC) and extracolonic cancer (stomach, duodenum, pancreas, and jejunum)

Etiology

  • Most commonly associated with germline mutations in SMAD4 (chromosome 18q) and BMPR1A (chromosome 10q) genes
  • An autosomal dominant condition with incomplete penetrance
  • Pathogenic mutation of at least 1 gene is found in 40%–50% of patients.

Pathophysiology

  • SMAD4 and BMPR1A genes exert a tumor suppression function. 
  • Mutations are most commonly germline-inherited defects, but can be de novo.
  • Mutations result in deficient tumor growth factor beta 1 (TGF-β) signaling and poor control of cell proliferation → uncontrolled cell proliferation → hamartomas → cancer

Clinical Presentation

History

  • Typically presents with:
    • GI bleeding
    • Intussusception
    • Obstruction
  • Patients may also complain of protrusion of a mass through the anal sphincter (rectal prolapse).
  • Symptoms of anemia: 
    • Fatigue
    • Generalized weakness
    • Loss of appetite
    • Cold hands or feet
    • Restless legs
    • Palpitations
    • Dyspnea

Physical examination

  • CNS:
    • Macrocephaly
    • Hydrocephalus
  • Thorax: 
    • Coarctation of aorta
    • Atrial septal defects
    • Tetralogy of Fallot
  • Urogenital tract: 
    • Undescended testes
    • Bifid uterus and vagina
    • Unilateral renal agenesis
  • GI tract: 
    • Meckel diverticulum
    • Malrotation
    • GI hemorrhage
    • Rectal prolapse

Diagnosis

Diagnosis is made by visualizing > 5 polyps on colonoscopy, or any number of polyps with a positive family history.

Imaging

  • Barium enema
  • Colonoscopy:
    • Polyps are typically round, red, and pedunculated.
    • Most patients will have from 50–100 colorectal polyps.
    • Usually limited to the distal colon and rectum, although can be found throughout the GI tract
Multiple pedunculated and sessile, non-bleeding juvenile polyps

Multiple pedunculated and sessile, nonbleeding juvenile polyps

Image: “Multiple pedunculated and sessile, nonbleeding polyps” by Amna Ahmed and Badr Alsaleem. License: CC BY 4.0

Management

Observation

  • Long-term follow-up due to increased risk of CRC
  • Colonoscopy: started at age 12–15 years
    • Can be started earlier if the patient becomes symptomatic
    • If negative: Repeat every 2–3 years.
    • If positive or polyps are removed: Repeat annually.
  • Upper endoscopy: started at age 15–25 years
  • Genetic testing of MADH4 or BMPR1A helps guide screening in at-risk family members.

Surgical management

  • Indicated in:
    • High-grade dysplasia
    • Patients who fail endoscopic management 
    • Prophylactic in patients unable to adhere to surveillance 
    • Rapid polyp formation
    • GI bleeding
    • Strong family history of CRC
  • Colectomy:
    • Limits hemorrhage associ­ated with polyp ulceration
    • Prevents mechanical obstruction
    • Prevention of cancer

Complications

  • Anemia
  • Bowel obstruction
Rectal obstruction x-ray

Rectal obstruction: Abdominal X-ray shows dilatation of proximal colon.

Image: “Abdominal X-ray shows dilatation of proximal bowel segments” by Katsikogiannis N, Tsaroucha A, Dimakis K, Sivridis E, Simopoulos C. License: CC BY 2.0

Prognosis

  • Lifetime risk of CRC: 39%–68% by age 60
  • Risk of gastric cancer: up to 21%

Differential Diagnosis

  • Familial adenomatous polyps (FAP): an autosomal dominant inherited genetic disorder that presents with numerous adenomatous polyps in the colon. Familial adenomatous polyps is the most common of the polyposis syndromes. All patients with FAP will develop colon cancer by age 35–40 years if left untreated. Management is with a surveillance program and colectomy.
  • Peutz-Jeghers syndrome: an autosomal dominant inherited disorder characterized by GI polyps and mucocutaneous pigmented macules. Peutz-Jeghers syndrome is caused by disruptions in the STK11 gene and is associated with colonic (colorectal) and noncolonic (pancreatic, gastric, breast, uterine, cervical, lung, ovarian, and testicular) cancers. Management is with close surveillance and surgery.
  • Cowden disease: an autosomal dominant disorder caused by mutations in the tumor suppressor gene PTEN, and characterized by the development of multiple benign hamartomas. The disease is a genodermatosis characterized by multiple benign hamartomas in any location, mucocutaneous lesions, and macrocephaly. Management depends on the location of the hamartoma. 
  • Hereditary nonpolyposis colon cancer: also known as Lynch syndrome; an autosomal dominant disorder caused by mutations in the mismatch repair (MMR) genes, which ultimately leads to the development of colorectal cancer in 1st-degree relatives. Management is with prophylactic colectomy and frequent endoscopy for surveillance. 
  • CRC: the 2nd leading cause of cancer-related deaths in the United States. Colorectal cancer is a heterogeneous disease, arising from genetic and epigenetic abnormalities, with influence from environmental factors. Almost all cases of CRC are adenocarcinoma. Most cases are asymptomatic, so screening is important. Diagnosis is by colonoscopy. Management is primarily surgical.
  • Thyroid cancer: malignancy of the thyroid gland cells, which can arise from the thyroid follicular cells or the calcitonin-producing C cells. Exposure to ionizing radiation and iodine deficiency are also considered risk factors. Diagnostic is with thyroid-stimulating hormone, ultrasound, and biopsy. Management is mainly surgical.

References

  1. Cohan, J.N., Varma, M.G. (2020). Large intestine. In Doherty, G.M.(Ed.), Current Diagnosis & Treatment: Surgery, 15e. McGraw-Hill. https://accessmedicine.mhmedical.com/content.aspx?bookid=2860&sectionid=241183142
  2. Shalkow, J. (2020). Colorectal Tumors in Adolescents and Young Adults. Emedicine. Retrieved June 20, 2021, from https://emedicine.medscape.com/article/993370-overview#a2
  3. Chung, D., Delgado, K. (2020). Juvenile polyposis syndrome. UpToDate. Retrieved June 21, 2021, from https://www.uptodate.com/contents/juvenile-polyposis-syndrome#H251243034

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