The prevalence of JPS is between 1/100,000 and 1/160,000.
Diagnostic criteria
In the absence of features suggesting a PTEN-related syndrome, JPS is diagnosed when one of the following is present:
- >5 juvenile polyps in the colon or rectum
- Juvenile polyps in other parts of the GI tract
- Any number of juvenile polyps and a positive family history
Other features:
Macrocephaly, hypertelorism, mental retardation, telangiectasia, haemangiomata, pulmonary arteriovenous fistulae, ventricular septal and other cardiac defects, thoracic skeletal anomalies, lipomata, hypospadias, genital freckling have all been described.
Genetics
Autosomal dominantly inherited mutations causing JPS occur in genes encoding components of the TGFβ signal transduction pathway:
SMAD4
SMAD4 is mutated in about 40% of families. The University of Utah hosts a SMAD4 mutation database. One recurrent ‘hotspot’ mutation, c.1372_1375delACAG, accounts for about half of SMAD4 cases, and 15–25% of all JPS.
15-22% of individuals with a SMAD4 mutation develop both hereditary haemorrhagic telangectasia and JPS, a condition termed JPS/HHT.
BMPR1A/ALK3
A further 40% of families harbour BMPR1A mutation (see variants database).
PTEN
Some patients have large chromosomal deletions encompassing both PTEN and BMPR1A.
PTCH
JPS type features are seen in rare families with basal cell naevus (‘Gorlin’) syndrome.
Risks
These are uncertain, and probably dependent on underlying gene. Malignant risk is from around 20y onwards and increases in the 4th decade. Overall risk of colorectal cancer by age 60y is estimated at up to 68% and gastric cancer 15–21%.
Management
Management of probands and proven mutation carriers
Proven surveillance strategies in JPS are not established, but several reviews with guidelines are available. Dunlop MG, Gut 2002 (download below) has recommended:
- 1–2 yearly colonoscopy from 15–18 years of age (or earlier if presenting with symptoms) until 35 years. From 35 years screening interval can be extended, but surveillance should continue until 70 years.
- Prophylactic surgery is a consideration. If polyps are found, remove and rescreen annually until polyp-free, then 3-yearly.
- 1–2 yearly upper GI endoscopy from 25 years of age.
- Consider cardiovascular examination and evaluation for HHT in SMAD4 mutation carriers.
Management of at-risk family members
In families where a mutation has not been found it has been recommended to perform upper and lower GI surveillance at least every 10y from age 15 until 45y.
Content updated 16 July 2019