Polyps occur in both the upper and lower gastrointestinal tract and exhibit a wide variety of shapes and sizes: Both flat and polyps that have a stalk occur, and their number ranges between only a few to over 100 polyps. Juvenile polyps (whereby “juvenile” refers to the histology and not the age of the patient) may develop from infancy to adulthood. Most JPS patients present with polyps by 20 years of age. Bleeding, which results in anemia, is a possible complication.
While most juvenile polyps are benign, they may progress to malignant tumors. By the age of 35, 17-22% of JPS patents suffer from colon cancer (colon carcinoma); and by the age of 60, 68% have colon cancer. The average age at diagnosis of colon carcinoma is 42. The probability of developing stomach cancer is 21% for JPS patients with polyps in the stomach.
JPS/HHT syndrome can occur in patients with a SMAD4 mutation and can be associated with symptoms of juvenile polyposis and HHT. HHT is a vascular disease and can manifest as nose bleeds, telangiectasia (vascular dilation of the capillaries in the skin), arteriovenous malformations (AVM, short-circuit connections between arteries and veins), or drumstick fingers. The clinical symptoms usually appear during early childhood, with AVM of the lungs and nose bleeds almost always occurring. Complications of JPS/HHT syndrome may include anemia, migraines, and headaches.
Moreover, a SMAD4-mutation may be linked to diseases of the main artery, such as bulges or a split in the aortic wall or even the dilation of the entire vessel. In addition, it is also possible for malfunctions of the mitral valve (the heart valve between the left atrium and the left ventricle) to occur.