Hamartomatous Polyps, Juvenile

Amitabh Srivastava, MD

Key Facts

Terminology

Hamartomatous polyp that may occur sporadically or as part of polyposis syndrome

Etiology/Pathogenesis

Germline mutations in SMAD4 or BMPR1A present in juvenile polyposis patients

Clinical Issues

Patients usually present at early age with anemia, diarrhea, or bleeding
Juvenile polyposis syndrome patients typically have between 50-200 polyps
Risk of colorectal cancer
Mean age for colon cancer in juvenile polyposis patients is ˜ 35 years
Risk is approximately 68% by 60 years of age

Macroscopic Features

JP patients usually have more than 50 polyps
Size is variable, but most measure around 1.0 cm in greatest dimension
Majority of polyps (> 2/3) are pedunculated

Microscopic Pathology

Marked expansion of lamina propria by loose, edematous, and inflamed stroma
Epithelial component is cystically dilated and shows variable degree of inflammation
Surface ulceration may be present
Gastric polyps resemble hyperplastic polyps or those seen in Cronkhite-Canada syndrome
Dysplastic change or carcinoma may be present in syndromic patients

Gross photograph shows multiple polyps in a patient with juvenile polyposis syndrome. The larger polyps

are pedunculated and multilobulated, while the smaller ones are sessile and smooth

Juvenile polyps are characterized by marked stromal expansion and cystically dilated crypts. The stroma is loose, edematous, and inflamed, while the cysts are filled with inspissated mucin

TERMINOLOGY

Abbreviations

Juvenile polyp (JP)
Juvenile polyposis syndrome (JPS)

Definitions

Hamartomatous polyp
- May occur sporadically
- May be manifestation of inherited familial polyposis syndrome
Patients with JPS have increased risk of colorectal carcinoma
No increase in cancer risk in sporadic JP

ETIOLOGY/PATHOGENESIS Genetics

Germline mutations in SMAD4 (DPC4) gene on 18q21 present in about 20% of JPS patients
- Exon 9 deletion is most common abnormality
- Patients with SMAD4 germline mutations more likely to have
  - Polyps in upper gastrointestinal tract
  - Positive family history
Germline mutations in BMPR1A gene on 10q23 present in similar proportion of JPS cases
- Variety of mutations have been identified in JP families
Mutations in SMAD4 and BMPR1A genes interfere with TGF-β signaling pathway

CLINICAL ISSUES

Presentation

Hematochezia
Anemia
Diarrhea
Prolapse
Juvenile polyps occur in distinct clinical settings
- Sporadic juvenile polyp
  - 90% of all polyps in children
  - 20-50% may have more than 1 polyp
  - No increase in risk of colorectal carcinoma
  - Polyps histologically identical to those in JPS patients
- Juvenile polyposis coli
  - Most common inherited form
  - Present clinically in 1st decade
  - Polyps confined to colon
- Generalized juvenile polyposis
  - Diffuse involvement of gastrointestinal tract
  - Colon, stomach, and small intestine involved
- Gastric juvenile polyposis
  - Rare form of disease
  - Polyps confined to stomach
  - Patients may present with protein-losing enteropathy and mimic Cronkhite-Canada syndrome
- Juvenile polyposis of infancy
  - Rare, autosomal recessive disease
  - Usually associated with death in infancy
Diagnostic criteria for juvenile polyposis syndrome
- More than 5 juvenile polyps (most patients have between 50-200)
  - Any number of polyps in patient with positive family history
- Extracolonic juvenile polyps are almost always syndromic
Extracolonic manifestations present in about 2/3 of JPS patients
- Macrocephaly, hydrocephalus, and mental retardation
- Congenital heart disease
- Pulmonary arteriovenous malformation
- Cleft palate and polydactyly
- Malrotation and Meckel diverticulum
- Cryptorchidism
Risk of colorectal cancer

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