Cap Polyposis

A rare colorectal disease characterized by multiple inflammatory polyps that predominantly affect the rectosigmoid area and that manifests primarily as rectal bleeding with abnormal transit, constipation and diarrhea.

Epidemiology

To date, around 67 cases have been described in the world literature. Females seem to be more affected than males.

Clinical description

The mean age at presentation is 49 years (range 5-79 years) with clinical manifestations including constipation alternating with periods of mucous and bloody diarrhea, associated with rectal bleeding, chronic straining with defecation, tenesmus, abdominal pain, fatigue, and loss of appetite and weight. Some patients may also show lower limb edema due to a protein-losing enteropathy.

Etiology

The etiology of Cap polyposis (CP) is still unclear but various causes including lower colonic mucosal prolapse, mucosal ischemia, inflammation, abnormal colonic motility, repeated trauma to the colonic mucosa caused by straining, infections (such as Helicobacter pylori infection), and immune disorders have been proposed.

Diagnostic methods

The diagnosis of CP relies on colonoscopy which reveals multiple polyps with white muco-fibrinoid caps and a normal intervening mucosa. The lesions are mainly located in the rectum and sigmoid colon. Pathological examination shows a polypoid lesion with an ulcerated cap of fibrin and mucus, elongated tortuous crypts filled with mucoid exudate, and possibly smooth muscle fibers in the mucosa. Laboratory findings may reveal hypoproteinemia, hypoalbuminemia, and severe anemia with low hemoglobin concentration. C-reactive protein (CRP) levels or white blood cell counts are mostly within the normal reference range.

Differential diagnosis

Differential diagnosis includes juvenile polyposis syndrome, Cronkhite-Canada syndrome (see these terms), amoebic dysentery, mucosal prolapse syndrome, and inflammatory bowel disease, primarily ulcerative colitis (with inflammatory polyps).

Management and treatment

CP has been treated empirically using sulfasalazine, 5-aminosalicylic acid, orally or anally administered steroids, metronidazole, quinolone, Helicobacter pylori eradication therapy and infliximab. For cases refractory to treatment, polypectomy (for fewer than 10 polyps) or surgical resection (for greater numbers of polyps) may be successful. Patients with predominant straining/constipation symptoms can be treated with laxatives.

Prognosis

CP is not a premalignant condition. The clinical course of CP ranges from spontaneous remission to a disease course requiring surgical resection of the affected bowel segments. However, the recurrence rates are high, particularly if numerous polyps are present.