Pulmonary cytolytic thrombi - A previously unrecognized complication of bone marrow transplantation

wLung injury is a frequent and severe complication of bone marrow transplan tation (BMT). Over the past 5 years we have recognized a new noninfectious pulmonary complication of allogeneic BMT in 12 patients, presenting with fe ver, pulmonary nodules on chest computed tomography, and distinctive histop athologic appearance descriptively termed "pulmonary cytolytic thrombi" (PC T). All but one patient were children transplanted fur malignant (9) and no nmalignant (3) conditions. Ten of the patients had active graft-versus-host disease (GVHD) of skin, bowel, or both at the time of diagnosis of the PCT . In all cases occlusive vascular lesions were present, most of them associ ated with hemorrhagic infarcts. The endothelial cell layer was discontinuou s in all cases stained with antibody to CD31. The thrombi had entrapped rec ognizable leukocytes and CD45-positive cell fragments embedded in a tenacio us basophilic material. The symptoms and radiologic findings resolved in we eks to months. PCT may represent a previously unrecognized form of pulmonar y acute GVHD.