Recurrent flu-like illness with migrating pulmonary infiltrates of unknown aetiology

Migrating pulmonary infiltrates present a difficult diagnostic and therapeutic challenge. We report on eight patients (mean age 51 years, range 32-78 years, with a prolonged history of migrating pulmonary infiltrates of unknown aetiology despite a very elaborate search for infectious causes, hypersensitivity pneumonitis or inhalation fever due to occupational or domestic exposure to fungi, or to other environmental causes, and for humoral or cellular immunological incompetence. These patients (one male, seven females) presented with recurrent episodes (mean 6, range 2-13) of a flu-like illness, often with cough, wheezing and pleuritic chest pain, but without systemic involvement. Previous medical histories were unremarkable. There was no relation with smoking habits, occupation, drug use or other possible exposures. Biochemical data were non-specific. There was no peripheral nor pulmonary eosinophilia; total IgE was normal, with negative RASTs and precipitins to a variety of antigens. Cultures and serological tests for bacteria, viruses, fungi, etc were non-contributory. Chest X-ray and computed tomography (CT) scan showed bilateral migratory pulmonary infiltrates, with a predilection for the middle and lower lung zones, often with a minor-to-moderate pleural effusion. Lung function tests were usually normal; at the most a slight decrease in diffusing capacity was noted in some patients. There was no or only a slight response to antimicrobials; systemic corticosteroids were not given. Further evolution was benign with patients being asymptomatic between the episodes. Despite elaborate investigations, the cause of these 'pneumonias' remains frustratingly unknown.