Pulmonary infarction characterized by bloody pleural effusion in a young male patient without underlying risk factors: a case report

Background Pulmonary infarction, caused by an obstruction of the pulmonary artery, sometimes occurs in young healthy individuals with pulmonary thromboembolism. Thoracentesis is rarely performed because of a small volume of pleural effusion in such cases. We report a case of pulmonary infarction initially diagnosed as bacterial pneumonia and pleurisy, exhibited bloody and exudative pleural effusion on thoracentesis later. Case presentation A 23-year-old male patient previously visited a medical institution after exhibiting left chest pain and bloody sputum for 1 week. The patient was initially diagnosed with bacterial pneumonia and started on oral antibiotics. Chest computed tomography scan revealed a small volume of pleural effusion in the left lung and an extensive consolidation in the left lower lung lobe. He was then diagnosed with left lobar bacterial pneumonia and pleurisy and was started on intravenous antibiotics. However, his condition worsened. After being referred to our hospital, the patient underwent thoracentesis, which revealed bloody and exudative pleural effusion. Deep vein thrombus and pulmonary artery thrombus were detected on contrast-enhanced computed tomography scan performed on the 5th day of admission. The patient was then diagnosed with pulmonary infarction caused by pulmonary thromboembolism, and treatment with anticoagulants was started. After the initiation of anticoagulation therapy, the symptoms and imaging findings gradually improved. Conclusions Pulmonary infarction caused by thromboembolism should be considered for bloody pleural effusion with chest pain and bloody sputum even in young people, particularly those without a predisposition to thrombosis.