Graft-versus-host disease of the gastrointestinal tract.

Gastrointestinal tract disease (GIT) is relatively common following bone marrow transplantation (BMT). Infections, particularly with viral agents, are similar to those affecting any immunosuppressed transplant recipient. However, two unique aspects of BMT are (a) cytotoxic damage caused by the chemotherapy and irradiation used to eradicate the patient's native marrow and (b) gastrointestinal involvement with graft-versus-host disease (GVHD). GVHD may affect any portion of the GIT; therefore, both upper and lower GIT biopsies may provide diagnostic information not evident in biopsy from a single site. The upper GI tract has a higher yield of positive biopsy specimens, but it is more difficult to biopsy. The basic histopathological feature of acute GIT GVHD, which occurs in the first 100 days posttransplant, is necrosis of individual cells in the regenerating compartment of the mucosa. Severe disease may lead to loss of crypts and eventual sloughing of the mucosa. The histology of acute GVHD may be simulated by cytoreductive agents and viral infections, particularly with cytomegalovirus (CMV). Therefore, an absolute biopsy diagnosis of acute GVHD cannot be made in the first 21 days posttransplant or in any mucosa containing CMV inclusions. The GIT is less often involved in chronic than in acute GVHD. The basic pathology of chronic GIT GVHD is fibrosis of the submucosa and subserosa. Therefore, mucosal biopsy is of limited usefulness in the diagnosis of chronic GVHD.