[Pleural effusion and eosinophilia associated with Metagonimus yokogawai infection].

We encountered a patient with a mild fever and chest discomfort in whom right pleural effusion and eosinophilia (48%) had developed. Parasite eggs were found in the feces, and metagonimiasis was diagnosed. The pleural fluid contained many Charcot-Leyden crystals, suggesting active eosinophilic inflammation. Metagonimus yokogawai usually occurs as a gastrointestinal parasite and causes only mild gastrointestinal symptoms such as diarrhea. Most cases of metagonimiasis resolve spontaneously. However, the main manifestation of metagonimiasis in our patient was pleural effusion. Some cases of idiopathic eosinophilic pleural effusion of unknown origin resolve spontaneously, as in our patient. Patients who are therefore considered to have idiopathic pleural effusion may include those with transient parasitic infection.