Pulmonary cytolytic thrombi: a previously unrecognized complication of bone marrow transplantation

Lung injury is a frequent and severe complication of bone marrow transplantation (BMT). Over the past 5 years we have recognized a new noninfectious pulmonary complication of allogeneic BMT in 12 patients, presenting with fever, pulmonary nodules on chest computed tomography, and distinctive histopathologic appearance descriptively termed "pulmonary cytolytic thrombi" (PCT). All but one patient were children transplanted for malignant (9) and nonmalignant (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 associated with hemorrhagic infarcts. The endothelial cell layer was discontinuous in all cases stained with antibody to CD31. The thrombi had entrapped recognizable leukocytes and CD45-positive cell fragments embedded in a tenacious basophilic material. The symptoms and radiologic findings resolved in weeks to months. PCT may represent a previously unrecognized form of pulmonary acute GVHD.