Cap polyposis of the colon: A report of 2 cases with unique clinical presentations but similar histopathologic findings

Cap polyposis is a rare, non-neoplastic disease characterized by multiple inflammatory polyps that are covered by a “cap” of fibrinopurulent granulation tissue and in most cases are located between the distal colon and the rectum. Patients usually present with bloody diarrhea, mucoid stools, and constipation. Endoscopically, mucosal polypoid structures are seen in the colon covered with a characteristic superficial, adherent white “cap” with normal intervening mucosa. Cap polyposis affects patients over a wide age range and, in rare instances, may also affect children. We report 2 cases of cap polyposis in the descending and rectosigmoid colon of a 6-year-old girl and in the rectosigmoid colon of a 61-year-old woman who have been followed for 8 and 6 years, respectively. Initial clinical examination and imaging, including computed tomography and colonoscopy revealed changes suspicious for inflammatory bowel disease and malignancy. Subsequent and repeated histopathological examinations however, revealed cap polyposis without definitive evidence of infection, chronic mucosal architectural changes, mucosal prolapse or dysplasia. We believe that this the first report of a pediatric patient with diffuse involvement of the descending and rectosigmoid colon by multiple inflammatory cap polyps mimicking inflammatory bowel disease. Furthermore, the unusual clinical presentation in both patients made the final diagnosis of cap polyposis challenging. When typical morphologic features of inflammatory-type polyposis present without evidence of mucosal prolapse, inflammatory bowel disease, inflammation or malignancy, a high index of suspicion for cap polyposis is warranted for timely recognition and treatment.