We report a case of inflammatory cap polyposis of the colon, a rare syndrome, affecting the rectosigmoid. It was observed in a context of mucous diarrhea. Endoscopic and radiological features consisted of elevated and umbilicated nodular lesions. Histology revealed polypoid lesions containing elongated crypts with superficial abrasions, covered by inflammatory and fibrinoid material. Etiopathogenesis of this new syndrome is unknown.