Olanzapine-induced eosinophilic pleuritis

An elderly patient, with a history of depression with psychosis, presented with breathlessness, a right exudative pleural effusion and a peripheral eosinophilia. The pleural fluid was eosinophil-rich (10% of leucocytes). Olanzapine therapy had been commenced 12 months previously. There was a family history of TB and the patient was of African origin. A full diagnostic work-up ensued including computed tomography of the thorax and local anaesthetic thoracoscopy. The pleura was unremarkable on CT and displayed bland smooth thickening at visual inspection during thoracoscopy. Pleural biopsies demonstrated chronic inflammation with eosinophils but no evidence of granulomatous inflammation or malignancy. Pleural tissue culture did not yield mycobacteria. A diagnosis of olanzapine-induced eosinophilic pleuritis was suspected and the pleural disease resolved with withdrawal of olanzapine. Eosinophilic pleural fluid is not a marker of non-malignant aetiology and eosinophilic pleural effusions require a careful and systematic diagnostic work-up. This is the second case report to identify olanzapine as a causative agent in eosinophilic pleural effusion.