Graft-versus-host disease-like syndrome in malignant thymoma

Allogenic transfusion of immunocompetent T lymphocytes into an immunodefici ent recipient is necessary for the development of graft-versus-host-disease (GVHD). The gastrointestinal tract is one of the most involved organs in h uman GVHD, and single-cell necrosis with apoptotic change and crypt abscess are characteristic histopathologic features. The thymus is important in im mune regulation, and dysregulation of the immune system can be expected onc e its microenvironment is disrupted. We report the case of a 38-year-old wo man with malignant thymoma without transplantation or transfusion history w ho initially presented with myasthenia gravis and clinically developed a GV HD-like syndrome with characteristic GVHD-like colitis on colonoscopy. We p ropose that disruption of the thymic microenvironment caused a dysregulated immune system and development of a GVHD-like syndrome.