A curious case of idiopathic eosinophilic pleural effusion post swimming pool diving

Eosinophilic pleural effusion is defined as pleural effusion with >10% eosinophil count. Even though the mechanism underlying eosinophilic pleural effusion is poorly understood, it is considered to be caused by pleural fluid sequestration of bone marrow-derived eosinophils. Even though there is a wide spectrum of diseases recognized to be associated with eosinophilic pleural effusion, including pleural irritation, trauma (hemothorax, pneumothorax, thoracic surgery), malignancy, parasitic infection, drug/toxin-induced and pulmonary embolism; almost 25% of cases remain idiopathic. We herein report a curious case of eosinophilic pleural effusion, which has developed post blunt trauma to the chest, sustained after diving into a swimming pool. The patient was extensively evaluated for possible etiologies but was found negative for any underlying known pathology that could lead to eosinophilic pleural effusion.