Kaposi's sarcoma of the colon in a young HIV-negative woman with Crohn's disease. We report a case of isolated colonic Kaposi's sarcoma in a 36-year-old HIV-negative woman with refractory Crohn's disease of the colon and perineum following 11 months' treatment with azathioprine. The clinical features of this case are quite different from those classically described in Kaposi's sarcoma. Among the known risk factors, iatrogenic immunosuppression would appear to be the most probable. 