GRAFT-VERSUS-HOST-LIKE COLITIS ASSOCIATED WITH MALIGNANT THYMOMA

A case of a patient with a malignant thymoma who developed an unusual form of colitis is reported. The patient was a previously healthy 20-y ear-old man who was referred to the Johns Hopkins Medical Institution for biopsy and resection of a mediastinal mass, which proved to be a m alignant thymoma. During this hospitalization and subsequently, the pa tient developed severe chronic diarrhea, the etiology of which remaine d uncertain after routine work-up, including cultures. Colonoscopic bi opsies revealed only minimal inflammation but numerous, prominent apop totic lesions within crypt epithelium, suggestive of an autoimmune or graft-versus-host-like colitis. The patient, who was immunocompetent a nd human immunodeficiency virus (HIV) negative, had no known risk fact ors for graft-versus-host-disease (e.g., no blood transfusions, no tra nsplantation history before diarrheal episodes). Stool cultures for pa thogenic bacteria and viruses were negative. The diarrhea and histolog ic findings eventually improved with steroid therapy yet returned on r ecurrence of the thymoma. This unusual form of colitis has not been pr eviously reported to be associated with thymoma and is interesting in light of the role the thymus plays in immune regulation.