Clozapine Induced Eosinophilic Pleural Effusion with Peripheral Eosinophilia After Two Years: A Case Report and Literature Review

There has been a steady increase in reports of clozapine causing eosinophilic pleural effusions (EPEs). For an effusion to be classified as eosinophilic it must have greater than 10% eosinophils, and is commonly associated with peripheral eosinophilia. Numerous etiologies exist for EPEs, and symptoms include dry cough, fever, chest pain, shortness of breath, and acute to chronic sputum production. The effusions are usually exudative and unilateral. When considering medication-induced EPEs, an extensive work-up should be done as it is a diagnosis of exclusion. If suspected, then the Naranjo probability scale can be applied. Despite the growing list of implicated medications, the pathophysiology of medication-induced EPEs remains unknown. Extensive literature review has provided some theories, with the most plausible postulating an acute allergic/hypersensitivity reaction. This is a case report of a 28-year-old male on clozapine for two years who suddenly developed shortness of breath with a large left-sided EPE and peripheral eosinophilia that resolved despite medication continuation.