Paragonimiasis Diagnosed Through Detection of Parasitic Ova in Pleural Effusion: A Clinical Case Report

Paragonimiasis, a chronic zoonotic parasitic infection caused by <i>Paragonimus</i> species, is frequently misdiagnosed due to its nonspecific clinical presentation and low disease awareness. We report a case of a 42-year-old male who was admitted following head and chest trauma. Initial chest CT revealed bilateral pulmonary contusions, a right rib fracture, and a significant pleural effusion, consistent with traumatic lung injury. Routine blood tests showed elevated white blood cells and neutrophils, but eosinophil counts remained within the normal range. Closed thoracic drainage was performed, and unexpectedly, numerous <i>Paragonimus</i> eggs and cholesterol crystals were identified in the pleural fluid. Subsequent serological testing confirmed positive parasite-specific antibodies, and genetic sequencing verified <i>Paragonimus</i> infection. Combined with epidemiological evidence from the patient's history, paragonimiasis was incidentally diagnosed in a patient who presented with a traumatic fracture and pleural effusion. The patient showed marked clinical improvement after treatment with praziquantel. This case underscores that normal eosinophil levels do not exclude paragonimiasis and that imaging findings can be misleading in the context of trauma. A thorough history-taking and comprehensive multimodal evaluation are essential for accurate diagnosis and management of pleural effusion in trauma patients to prevent oversight or misdiagnosis.