Pleural Toxocariasis Presenting as Eosinophilic Pleural Effusion: A Case Report

Eosinophilic pleural effusion (EPE) is a rare pleural disorder characterized by a significant proportion of eosinophils in the pleural fluid. Its etiologies are diverse and include malignancy, infections, pulmonary embolism, drug-induced reactions, and parasitic diseases. Pleural involvement in toxocariasis is rare and may pose diagnostic challenges, particularly in tuberculosis-endemic regions. We report the case of a 67-year-old male farmer from a rural area who presented with progressive dyspnea, right-sided chest pain, fever, and general deterioration. Physical examination revealed signs consistent with a right pleural effusion. Laboratory investigations showed leukocytosis with peripheral eosinophilia (1,040/μL; reference range: 0-500 cells/μL) and elevated inflammatory markers. Chest imaging demonstrated a loculated right pleural effusion. Pleural fluid analysis revealed an exudative effusion with marked eosinophilia. Microbiological investigations, including bacterial cultures and acid-fast bacilli testing, were negative, although pleural tuberculosis could not be completely excluded based on microbiology alone. Cytological examination showed no malignant cells; however, a single negative cytology does not fully exclude malignancy. Despite pleural drainage and empirical broad-spectrum antibiotic therapy, no sustained clinical improvement was observed. Further investigations revealed elevated anti-Toxocara canis IgG levels in both serum and pleural fluid, confirmed by Western blot analysis. Given the clinical context of EPE, negative microbiological workup, and persistent eosinophilia, these findings supported a diagnosis of pleural toxocariasis, although seropositivity may also reflect prior exposure. Treatment with albendazole was followed by clinical and radiological improvement, with resolution of eosinophilia and marked regression of the pleural effusion. This case highlights the importance of including parasitic infections, particularly toxocariasis, in the differential diagnosis of EPE. In tuberculosis-endemic regions, careful evaluation is required to avoid premature diagnostic closure. Albendazole therapy may be associated with clinical improvement in selected cases; however, causality cannot be definitively established from a single case report.