Rounded atelectasis complicated by obstructive pneumonia and pulmonary arterial thrombosis [published erratum appears in Chest 1991 Jun;99(6):1556] A patient with a history of asbestos exposure developed rounded atelectasis. The mass was associated with local bronchial obstruction, obstructive pneumonia and arterial thrombosis. Autopsy demonstrated marked pleural thickening and radiographically inapparent asbestosis. This is the first reported case in which seemingly benign rounded atelectasis not only increased morbidity, but also contributed to mortality through airway obstruction and local arterial thrombosis. 