Acute eosinophilic pneumonia associated with mefloquine prophylaxis: A case report.

Background: Eosinophilic pneumonia is a rare but potentially life-threatening condition characterized by eosinophilic infiltration of the lung parenchyma, which can present as acute respiratory failure. Drug-induced eosinophilic pneumonia (DIEP) has been associated with several medications, though the pathophysiological mechanisms remain incompletely understood. Among antimalarial agents, mefloquine has rarely been implicated in severe pulmonary adverse effects. Case presentation: We report the case of a 34-year-old previously healthy female who developed acute respiratory failure after completing a prophylactic regimen of mefloquine for malaria prevention. The patient initially presented with fever, dyspnea, and hypoxemia, rapidly progressing to severe respiratory distress requiring invasive mechanical ventilation. Laboratory tests revealed marked eosinophilia, while thoracic computed tomography (CT) demonstrated diffuse ground-glass opacities and nodular infiltrates. Bronchoalveolar lavage (BAL) was positive for Rhinovirus, suggesting a possible interplay between drug-induced hypersensitivity and viral infection. Following corticosteroid therapy and supportive care, the patient's condition improved, with resolution of eosinophilia and radiological abnormalities. Discussion: This case highlights the need for heightened clinical suspicion of mefloquine-induced eosinophilic pneumonia in patients presenting with unexplained respiratory symptoms following antimalarial prophylaxis. The pathogenesis may involve immune-mediated reactions and oxidative stress, potentially exacerbated by concurrent infections. Conclusion: Mefloquine should be considered a potential cause of acute eosinophilic pneumonia, particularly in patients with recent drug exposure. Early recognition and timely management, including drug discontinuation and corticosteroid therapy, are crucial to preventing severe complications and ensuring favorable outcomes.