Juvenile polyposis syndrome (ORPHA:2929)
A rare condition characterized by the presence of juvenile hamartomatous polyps in the gastrointestinal (GI) tract.
Epidemiology
Annual incidence is estimated at between 1/100,000 and 1/15,000.
Clinical description
Polyps may develop at any age from infancy through to adulthood, with most affected individuals presenting polyps by adolescence/early adulthood. A diagnosis of JIP is made on the basis of one or several of the following findings: the presence of more than five juvenile polyps in the colon and/or rectum; the presence of juvenile polyposis throughout the digestive tract, including the stomach; the presence of any number of juvenile polyps in association with a family history of JIP. Several types of JIP have been described, including three forms that differ on the basis of the location of the polyps (generalized juvenile polyposis of the upper and lower GI tract, juvenile polyposis coli and juvenile polyposis of the stomach) and a more severe infantile form, juvenile polyposis of infancy (see this term). Regardless of the subtype, the clinical signs of JIP are isolated rectal bleeding, anemia, abdominal pain, intussusceptions and diarrhea. Rectal prolapse and spontaneous anal elimination of polyps have been noted in juvenile polyposis coli and generalized juvenile polyposis. Other associated signs may include growth delay and edema.
Etiology
JIP is transmitted in an autosomal dominant manner and mutations in the SMAD4 (18q21.1) and BMPR1A (10q22.3) genes have been associated with the disease. However, no genetic anomalies have been identified so far in around 60% of the cases. A few genotype-phenotype correlations have been established: the frequency of gastric polyposis is higher in SMAD4 carriers than in BMPR1A carriers and the association of JPS with hereditary hemorrhagic telangiectasia (juvenile polyposis/hereditary hemorrhagic telangiectasia syndrome) is observed in just under a quarter of SMAD4 mutation carriers.
Diagnostic methods
Diagnosis is based on the clinical findings, family history, endoscopic findings and histological analysis of the polyps. Molecular genetic testing may also be useful for confirming the diagnosis in carriers of SMAD4 and BMPR1A gene mutations.
Differential diagnosis
The differential diagnosis should include other syndromes associated with polyposis including Cowden syndrome and Bannayan-Riley-Ruvalcaba syndrome, familial adenomatous polyposis and Peutz-Jeghers syndrome (see these terms).
Management and treatment
Management should involve routine colonoscopy and if the number of polyps remains low endoscopic polypectomy is the gold standard for treatment. Due to the risk of cancer and polyposis extension, surgical colectomy associated with protectomy and ileoanal anastomosis may also be proposed.
Prognosis
The prognosis of JIP is based on the risk of developing GI or pancreatic cancer after 20 years of age. The cumulative risk for developing cancer in patients with JIP is 20% at the age of 35 years and 68% after the age of 60 years. The risk of cancer is higher among individuals with generalized juvenile polyposis.

                            Last update: 
                            January 2009


                            - Expert reviewer(s): 
                            Pr Frédérique SAUVAT