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Cap polyposis

Amy Lo, MD
Young-Mee Lee, MD
Section Editor
John R Saltzman, MD, FACP, FACG, FASGE, AGAF
Deputy Editor
Anne C Travis, MD, MSc, FACG, AGAF


Cap polyposis is a rare condition characterized by mucoid, bloody diarrhea associated with erythematous, inflammatory colonic polyps covered by a cap of fibrinopurulent mucous. The disorder was first described in 1985 and has subsequently been reported in occasional case series [1,2]. Despite its rarity, recognition is important since its clinical symptoms may be similar to inflammatory bowel disease or irritable bowel syndrome.


The epidemiology of cap polyposis has not been well studied. It occurs predominantly in women, most frequently during the fifth decade of life. However, it has been described in men and women ranging from 12 to 76 years of age [1,3,4].


The etiology is not well understood. It was initially considered a form of inflammatory bowel disease [1]. Others suggested an infectious origin such as Helicobacter pylori or Escherichia coli O18 [3,5], based in part upon symptomatic and colonoscopic improvement after treatment with antibiotics [3,6,7]. Cap polyposis has also been described following pelvic surgery [5].

A possible association with mucosal prolapse syndrome (MPS) has been suggested based upon similar histologic features [8-10]. In MPS, mucosal prolapse occurs adjacent to tumors, diverticula, and prolapsed colostomies. Similarly, abnormal colonic motility may result in mucosal prolapse at redundant transverse folds resulting in local ischemia, recurrent mucosal trauma, and the development of cap polyposis [11]. Symptomatically, the abnormal colonic motility results in constipation.


Erythematous, pedunculated, or sessile polyps are found typically in the rectosigmoid colon, but may involve the entire colon [12,13]. The polyps are usually located at the apices of enlarged transverse mucosal folds and can number from a few to many [1]. They are often mistaken for inflammatory pseudopolyps. The lesions have a reddish surface with adherent mucous and occasional white specks in the colonic mucosa surrounding them [3,14]. There can be associated central pitting and the typical white mucoid cap. The intervening mucosa is normal. A mild form of the disease has been described characterized by multiple patches of flushed, edematous mucosa separated by normal mucosa [3]. Whether these patients progress to the more classic form is unclear.


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Literature review current through: Nov 2016. | This topic last updated: Wed Sep 28 00:00:00 GMT+00:00 2016.
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