In December 2002, a 64-year-old woman was referred to our department with a diagnosis of empyema. Twenty days previously, she had a sudden onset of right-sided pleuritic chest pain. On the same day, she visited a physician, who hospitalized her with a diagnosis of pneumonia and administered antibiotics. The chest radiographs and chest CT scan demonstrated loculated collections of pleural fluid. When she deteriorated, she was referred to our department, at which time she complained of right-sided pleuritic chest pain. The chest radiograph demonstrated a pleural-based opacity in the right upper hemithorax, a homogenous opacity in both the mid and lower right hemithorax, and blunting of the right costophrenic angle. Thoracentesis revealed a serosanguineous, lymphocyte-predominant exudate (Table 1) with no organisms and negative cytology. Spiral CT angiography revealed hypodense plaques within the lumina of both the right main pulmonary artery and its ascending branch (Fig 6
). V̇/Q̇ scintigraphy demonstrated segmental perfusion defects in the apical and posterior segments of the right upper lobe, and in the mediobasal and posterobasal segments of the right lower lobe, all with matched ventilation defects. Duplex ultrasonography revealed left femoral vein thrombosis. Echocardiography revealed that the pulmonary artery pressure was approximately 30 mm Hg. The patient was treated with subcutaneous enoxaparin sodium (Clexane), 1.0 mg/kg twice daily. Warfarin was added on the second hospital day. There was progressive resolution of the opacities on successive chest radiographs, and the findings of the chest radiograph that was taken after 3 months of treatment were normal. There were no significant events during the follow-up period of 6 months.