DIFFUSE INFILTRATIVE DISEASES OF THE LUNG



A large number of lung diseases are character­ized by the replacement or infiltration of normal lung by abnormal tissue (Fig. 20-1). On rare oc­casions, the insulting agent may be well recog­nized, as in silicosis, although more often the cau­sative process is unknown and only the response is obvious. The insult may cause lung injury by direct toxicity, as a result of an inflammatory re­sponse, or through an immunologically mediated reaction. Regardless of the mechanism of injury the influx of inflammatory cells into the lung in-terstitium, perivascular space, and alveolar space results in the development of an alveolitis or vas­culitis and if carried to completion, lung fibrosis.