Polyps, Intestinal

Basics

Description

  • Intestinal polyps are abnormal tissue growths protruding from the intestinal mucosa into the lumen.
    • Most common in children are solitary juvenile polyps, but these may also be multiple in number.
    • May be associated with various polyposis syndromes
  • Classified by gross appearance
    • Pedunculated: mushroom-like and attached to mucosa with a narrow stalk
    • Sessile: elevated, flat lesions broadly attached to mucosa
  • Types of polyps:
    • Hamartomas
    • Adenomatous
  • Hamartomatous polyps
    • Juvenile polyps: usually a solitary polyp
    • Juvenile polyposis syndrome (>3 to 5 juvenile polyps or any number of juvenile polyps with a positive family history)
      • Juvenile polyposis of infancy
      • Juvenile polyposis coli (colonic involvement only)
      • Generalized juvenile polyposis (small bowel and colonic involvement)
    • Peutz-Jeghers syndrome
    • Cowden syndrome
    • Bannayan-Riley-Ruvalcaba syndrome (BRRS)
  • Adenomatous polyps
    • Familial adenomatous polyposis (FAP)
      • Severe form and attenuated forms
    • Gardner syndrome (colonic polyps with osteomas and epidermal inclusion cysts)
    • Turcot syndrome (colonic polyps with brain tumors)
  • Other polyposis syndromes
    • MUTYH-associated polyposis syndrome
    • Serrated polyposis syndrome

Epidemiology

  • Juvenile polyps are the most common childhood polyps:
    • Account for >90% of polyps seen in children
    • 1–2% of asymptomatic children are estimated to have juvenile polyps.
    • Typically present between 2 and 5 years of age
    • Twice as common in boys than girls
    • >5 juvenile polyps should raise clinical suspicion for juvenile polyposis syndrome.
  • Adenomatous polyps in FAP may present in early childhood or adolescence with an average age of onset of 16 years.

Prevalence

  • Juvenile polyposis syndrome: 1 in 100,000 to 1 in 160,000
  • Peutz-Jeghers syndrome: 1 in 25,000 to 1 in 300,000
  • FAP: 1 in 5,000 to 1 in 17,000

Risk Factors

Family history of polyposis syndrome

Genetics

Different genes and inheritance patterns with various polyposis syndromes:

  • Juvenile polyposis syndrome
    • Autosomal dominant with variable penetrance
    • Mutations in SMAD4 and BMPR1A genes, involved in transforming growth factor-β (TGF-β) signal transduction
    • SMAD4 mutation also associated with hereditary hemorrhagic telangiectasia and arteriovenous malformations
  • Peutz-Jeghers syndrome
    • Autosomal dominant
    • Mutations in STK11/LKB1 tumor suppressor gene are associated.
  • Cowden syndrome and BRRS
    • Autosomal dominant
    • Associated with mutations in PTEN gene
  • FAP
    • Autosomal dominant
    • Mutation in adenomatous polyposis coli (APC) tumor suppressor gene

Pathophysiology

Mutations in tumor suppressor genes likely lead to dysregulation of cell proliferation and apoptosis in polyposis syndromes.

Commonly Associated Conditions

  • Juvenile polyposis syndrome, Cowden syndrome, and BRRS all have juvenile polyps as part of their manifestations.
    • Cowden syndrome is associated with colonic and gastric polyps with extraintestinal symptoms including mucocutaneous lesions, thyroid adenomas and goiter, fibroadenomas and fibrocystic disease of the breast, uterine leiomyomas, and macrocephaly.
    • BRRS is associated with colonic and ileal polyps.
  • Peutz-Jeghers syndrome is characterized by multiple gastrointestinal (GI) pedunculated hamartomatous polyps.
  • FAP, Gardner, and Turcot syndrome are characterized by multiple adenomatous polyps.

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