Juvenile polyposis syndrome, also known as familial juvenile polyposis, is a hereditary genetic syndrome. It is usually transmitted in an autosomal dominant fashion, but may be due to a new mutation in a quarter of cases.
Juvenile polyposis may occur in any of three types:
- Infantile juvenile polyposis: the infant has numerous polyps in the intestines or stomach . The affected child often develops a condition called protein-losing enteropathy, which leads to severe malnutrition, wasting, and failure to thrive despite adequate feeding.
- Generalized juvenile polyposis: in these patients, polyps are present in the intestines or stomach during childhood
- Juvenile polyposis coli: Similar to generalized juvenile polyposis, but the polyps in this case are confined to the colonic mucosa.
Juvenile polyposis syndrome often has no symptoms. When symptoms are present, hey may include:
- Bleeding from the rectum
- Anemia with tiredness or pallor due to significant bleeding in stools
- A change in bowel habits such as constipation or diarrhea
A physical examination may show the presence of a large polyp. In this and all other cases, a barium enema or colonoscopy is required to show the presence of multiple polyps. The family history is also important, as many cases are inherited, though in other patients, the mutation is a new one.
Juvenile polyposis syndrome can be diagnosed based on the following findings: :
- More than five polyps are found in the rectum or in the colon.
- Juvenile polyps located elsewhere in the gastrointestinal tract
- A family history of juvenile polyps combined with a clinical finding of any numer of polyps in an infant or child
The polyps are usually visualized on screening high-risk patients, or symptomatic patients. A colonoscopy is typically offered, consisting of the passage of a flexible thin endoscopic tube through the rectum. Once polyps are seen, a biopsy can also be carried out. Histopathological examination of biopsied tissue shows that the polyps are hamartomatous, which means they are made up of normal tissue elements assembled abnormally. Thus the polyps are composed of normal epithelium, with a smooth surface, showing dilated mucus-filled glands. The stroma is dense and inflammatory cells are present.
Other tests that are usually offered include:
Here a barium sulfate solution, which is radio-opaque, is given to the patient through the rectum. It outlines the mucosal lining on X-rays, and confirms the presence of polyps. Biopsies will still require a colonoscopy, however.
Stool occult blood
In patients without symptoms, bleeding in the gastrointestinal tract may be a sign of polyps.
Diagnosis is confirmed by molecular genetic testing, such as sequencing analysis and deletion/duplication analysis. The genes usually tested are the BMPR1A and the SMAD 4 genes, which are abnormal in about 20% each of patients with the condition. Pathogenic variants of the ENG gene have not yet been identified as causative for the condition, in patients who lack the above gene mutations. About 60% of cases have no known mutation.
The BMPR1A mutation has been shown to occur in up to a quarter of patients, while half of them have a mutation in the SMAD 4 gene. In most cases the latter is associated with evidence of hereditary hemorrhagic telangiectasis, which presents with nose bleeds.
Reviewed by Catherine Shaffer, M.Sc.