Possible involvement of an environmental agent in the development of acute eosinophilic pneumonia

Background: Although the pathogenesis of acute eosinophilic pneumonia remains largely unknown, it has been suggested that it may include a hypersensitivity phenomenon induced by inhaled environmental antigens. Methods: To investigate this possibility, we studied the effect of environmental challenges in three patients with acute eosinophilic pneumonia. Symptoms and laboratory findings were evaluated before and after the challenge tests in the patient's homes and their places of work. Results: After the provocation challenges to their homes, all three patients developed fever, cough, and fatigue and two of them presented with dyspnea. Inspiratory crackles became audible in all cases, and there was a decreased Pao2 level in two. Similar challenges at their workplaces were negative. After moving out of their homes, the patients engaged in their usual work but had no recurrent episodes. Conclusions: These results suggest that environmental factors in the home can be the cause of acute eosinophilic pneumonia. In order to elucidate the pathogenesis of the disease, it is important to further investigate environmental factors.