[Pulmonary dirofilariasis with cavity formation and pleural effusion].

A 61-year-old man visited a community hospital because of hemosputum. A solitary nodule in the left lower lung field was pointed out on a chest roentgenogram. The patient was treated with antibiotics, but the solitary nodule increased in size. He was referred to our hospital because of high fever and observations of cavity formation and pleural effusion on a chest roentgenogram. The pleural effusion showed no cytologic evidence of malignancy, and cultures were also negative for bacteria. An increased percentage of lymphocytes was detected in the pleural effusion, but slight eosinophilia was found in blood samples. Dot enzyme-linked immunosorbent assay and Ouchterlony's double-diffusion test yielded a diagnosis of pulmonary dirofilariasis. After drainage of the pleural effusion by thoracentesis, spontaneous regression was observed. Cavity formation, pleural effusion, and spontaneous regression are in general rare in patients with pulmonary dirofilariasis.