Bronchiolitis fibrosa obliterans.

Bronchiolitis fibrosa obliterans, described first by Lange in 1901, is an obliterative process of the bronchioles in which there is extensive damage to the bronchial wall involving all the constituent elements (the epithelium, elastic tissue, and muscle fibres), and the lumen is partially or totally occluded by bronchial exudate organized by fibroblasts and capillaries. The disease is extremely rare in man. LaDue (1941), for example, made a specific search of this entity in necropsy material and encountered but one case in 42,038 consecutive necropsies. On the other hand, in experimental dogs which had been exposed to war gases, such as phosgene, chloropicrin, and chlorine, Winternitz (1920) found the disease consistently. Even in humans, the majority of described examples are due to the inhalation of poisonous gases. Statements that the disease is not uncommon are based on the confusion of the diffuse widespread disease with an occasional histological finding of a bronchiolus with organized exudate (Ehrich and McIntosh, 1932). The aetiology (McAdams, Jr., 1955; Blumgart and MacMahon, 1929; Amoroso and McNally, 1949; Loblich, 1952) of this pathological entity is clear when it is associated with the inhalation of toxic gases capable of chemically damaging the elements of bronchiolar walls. Among those most commonly reported are oxides of nitrogen (NO2 and N204, both of these being readily soluble in water, thus forming nitric acid), war gases such as have been mentioned above, and occasionally other types of gases such as chlorine. A few examples have been directly related to pulmonary infection, such as infection by Pfeiffer's bacillus (Hiibschmann, 1916) or whooping cough (Blumgart and MacMahon, 1929), and occasionally to aspiration of a foreign body (Wegelin, 1908), while a few others have been of unknown or uncertain aetiology in which the patient was neither exposed to toxic gases nor had clinical evidence of pulmonary infection. The latter group has been called 'primary bronchio-