[A case of Kaposi's sarcoma of the rectum presenting with hematochezia and rectal pain].

: A man in his 20s was referred to our hospital with hematochezia and rectal pain. Total colonoscopy revealed a reddish, protruding, ulcerated lesion occupying approximately half of the luminal circumference of the rectum. Examination of biopsy specimens showed proliferating spindle cells infiltrating the lamina propria, a finding consistent with Kaposi's sarcoma. The patient was also found to be anti-human immunodeficiency virus (HIV) antibody positive;therefore, we diagnosed acquired immunodeficiency syndrome (AIDS). The lesions of Kaposi's sarcoma were also seen in the skin, lung, and lymph nodes, but there were no lesions elsewhere in the gastrointestinal tract other than the rectum. We started anti-HIV therapy and chemotherapy against these lesions, and the lesions subsequently reduced in size. We present a rare case of a man with Kaposi's sarcoma presenting with a rectal lesion.