Cap polyposis is a rare and benign colorectal disease first described in 1985. It is characterized by multiple inflammatory polyps with a cap of granulation tissue near to the surface. We report the case of a 71-year-old man with cap polyposis who required surgical intervention. A review of literature is given.
Our patient suffered from severe bloody diarrhoea. Endoscopy revealed multiple sessile polypoid lesions of the mucosa in the rectum and the sigmoid colon. Anorectal manometry did not show any evidence of mucosal prolapse.
Initially, in several endoscopic sessions a complete polypectomy was intended. Since the disease was only temporarily responsive to antiphlogistics and abdominal symptoms worsened, a left hemicolectomy including part of the rectum had to be performed. Examination of the resected gut and of biopsies showed typical histological features of cap polyposis: sessile polyps with elongated crypts and a granulation tissue 'cap' near to the surface of the partly ulcerated mucosa. The epithelium of the crypts had saw-tooth configurations like in hyperplastic polyps without evidence of adenomatous changes. In the lamina propria signs of fibromuscular obliteration were found: moderate hyperplasia of smooth muscle fibers and mild fibrosis. Between the polyps the mucosa was normal.
Pathogenesis of cap polyposis which affects both genders of a wide range of age remains still unclear. In many patients abnormal colonic motility and straining at defecation seems to be responsible for shearing stress and prolapse of the mucosa resulting in the development of polyps with fibromuscular obliteration of the mucosa, which can be found in other gastrointestinal conditions of prolapsing mucosa as well. Infection has also been discussed as a possible cause. Until now no infective organisms have been detected in the affected gut but there are four reported cases of cap polyposis that were cured by eradication therapy for Helicobacter pylori found in the stomach.