CASE PRESENTATION: A 50 year old male with PMH of HTN and gout, presented with 2 month history of gradually worsening dyspnea. He reported no other symptoms. He was started on Allopurinol for gout 6 months ago.Vitals were stable except for tachypnea of 30 breaths/minute. Physical exam was only remarkable for right sided decreased breath sounds. CXR (fig 1A)showed large right pleural effusion. CT chest ruled out any parenchymal disease(fig 1B). Routine laboratory workup was normal. Thoracentesis yielded 1.5 liter of amber colored fluid. Analysis confirmed an exudative pleural effusion with predominance of eosinophils (40%). His symptoms improved. Thoracentesis was repeated next day and further 1200 ml fluid was removed. Diagnostic testing of the pleural fluid failed to identify any infectious, rheumatological or cancerous process. Negative workup, pleural fluid eosinophilia and temporal relationship between allopurinol initiation and development of pleural effusion suggested drug induced EPE. Allopurinol was replaced with Rasburicase and he was discharged home. A week later, an outpatient pleural biopsy was performed, reported negative. Follow up CT chest 4 weeks later showed only a small effusion (fig 1C), which disappeared completely 6 months after stopping Allopurinol.