Ultrastructure of the lung in Loeffler's pneumonia.

A case is presented fulfilling the diagnostic criteria of "Loeffler's eosinophilic pneumonia". No etiologic factors could be determined, and the chest roentgenogram returned to normal. Lung biopsy at the peak of the disease demonstrated an interstitial eosinophilic pneumonia without tissue necrosia or vasculitis. By electron microscopy, the alveolar capillary basement membranes were intact and exhibited no immune deposits. Normal appearing eosinophils were abundant in the alveolar capillaries, interstitium and alveolar spaces. Occasional eosinophils released their granules within the alveolar wall. Macrophages were increased in number in both the alveolar wall and alveolar spaces.