Reactive airways dysfunction syndrome presenting as a reversible restrictive defect.

A 25-year-old farm worker developed acute bronchopneumonia after heavy exposure to a respiratory irritant in a silo. He recovered from the acute episode but then experienced chronic dyspnea and fatigue. Pulmonary function testing showed small lung volumes with a normal ratio of 1 s forced expiratory volume/forced vital capacity (restrictive defect). This defect improved markedly with bronchodilator treatment and changed to a mixed obstructive/restrictive defect with methacholine challenge. We believe that this is an example of the reactive airways dysfunction syndrome manifested by a restrictive rather than obstructive defect. Constriction of airways at the bronchiole or alveolar duct level is the most likely cause of the syndrome.