[A rapidly progressive case of mediastinitis in which the patient developed inflammation of the soft tissue surrounding the pulmonary artery].

A 51-year-old male patient with no underlying illness developed a fever of 38-39 degrees C in June 2009. The fever persisted for 4 days and, because elevated hepatobiliary enzymes, leukocytopenia and thrombocytopenia were observed, along with chest CT findings of inflammation of the soft tissues surrounding the left pulmonary artery, the patient was admitted for further examination. Three days after admission, the patient's blood pressure rapidly decreased, resulting in respiratory failure. Rapid proliferation of the soft tissue surrounding the pulmonary artery and mediastinum was observed on an emergency chest CT. Malignant lymphoma was initially considered as a possible differential diagnosis; however, neither pleural effusion nor infiltration of malignant cells could be observed on bone marrow examination. In addition, because the patient responded well to antibiotics, a diagnosis of acute mediastinitis was reached. Mediastinal drainage was not performed because the quantity of accumulated fluid was small and because the patient, both in terms of his clinical symptoms and imaging results, showed improvement with the continuation of antibiotics alone. The patient was ambulatory and was discharged after 24 days of hospitalization. Acute mediastinitis often follows a rapidly progressive and fatal course without specific symptoms. In the event of unknown infection following an aggressive course, as in the present case, acute mediastinitis must be considered with the goal of early diagnosis and treatment.