Several to dozens of polyps, develop mainly in the colon, and can develop in the upper alimentary tract.
The polyps vary in size, large polyps are predisposed to be pendulous, and bleeding or erosions are often associated with this on the surface.
The number and shape of polyps are similar to those of polyps of Peutz-Jeghers syndrome.
In their histologies, inflammatory cell infiltration in rich lamina propria mucosae and interstitium is pathognomonic, and dilated grand ducts are scattered among them.
Usually, however the grand ducts do not have an aberrant type, in some cases the adenomatous gland tract can be scattered in a part of polyps, and also the cases with complications of cancers were reported. Also, the disease has familial incidence and non-familial incidence, and the former frequently develops many colorectal cancers in the families.
Non-familial cases tend to be associated with congenital malformation.