Polyps are found throughout the GI tract (most frequently in the stomach and large intestine, followed by the small intestine) though typically avoid the esophagus. A biopsy will reveal them to be hamartomas; the possibility that they progress to cancer is generally considered to be low, although it has been reported multiple times in the past. Chronic diarrhea and protein-losing enteropathy are often observed. Possible collateral features include variable anomalies of ectodermal tissues, such as alopecia, atrophy of the nails, or skin pigmentation
Cronkhite–Canada syndrome
Ardalan–Shoja–Kiuru syndrome
Zamzam–Sheriff–Phillips syndrome
Grinspan's syndrome
Worster-Drought syndrome
Hapnes Boman Skeie syndrome
Laugier–Hunziker syndrome
Cohen syndrome