Cap polyposis: an unusual cause of rectal bleeding in a young patient

A 28-year-old previously healthy man presented with rectal bleeding. Laboratory studies revealed a hemoglobin of 6.8 g/dL with an iron deficiency profile, for which he received 1 unit of packed red blood cells and was referred for a gastroenterology evaluation. Colonoscopy showed a 4-cm-long circumferential, polypoid, fungating, and friable rectal mass at the anal verge (A). Examination of a biopsy specimen revealed severe inflammation, but adequate crypt architecture was not visualized. Subsequently, he underwent complete surgical excision of the mass, and histopathologic analysis revealed inflammatory infiltrate, covered by an ulcerated mucosa and a surface exudate (“cap”), consistent with cap polyposis (B, low-power view, H&E, orig. mag. ×10) and (C, medium-power view, H&E, orig. mag. ×40). A few weeks later, his hemoglobin improved to 15.3 g/dL. Follow-up flexible sigmoidoscopy showed a 7-mm distal rectal polyp, which was resected and showed similar histologic characteristics. He continues to do well.