Ref: Textbook of pathology (Harsh Mohan) 6th edition, page No.481 Morphology of Individual Types of Emphysema CENTRIACINAR (CENTRILOBULAR) EMPHYSEMA. Centriacinar or centrilobular emphysema is one of the common types. It is characterised by initial involvement of respiratory bronchioles i.e. the central or proximal pa of the acinus. This is the type of emphysema that usually coexists with chronic bronchitis and occurs predominantly in smokers and in coal miners' pneumoconiosis. 2. PANACINAR (PANLOBULAR) EMPHYSEMA. Panacinar or panlobular emphysema is the other commontype. In this type, all poions of the acinus are affected but not of the entire lung. Panacinar emphysema is most often associated with a1-antitrypsin deficiency in middle-aged smokers and is the one that produces the most characteristic anatomical changes in the lung in emphysema. PARASEPTAL (DISTAL ACINAR) EMPHYSEMA This type of emphysema involves distal pa of acinus while the proximal pa is normal. Paraseptal or distal acinar emphysema is localised along the pleura and along the perilobular septa. The involvement is seen adjacent to the areas of fibrosis and atelectasis and involves upper pa of lungs more severely than the lower. This form of emphysema is seldom associated with COPD but is the common cause of spontaneous pneumothorax in young adults. Grossly, the subpleural poion of the lung shows air-filled cysts, 0.5 to 2 cm in diameter. 4. IRREGULAR (PARA-CICATRICIAL) EMPHYSEMA. This is the most common form of emphysema, seen surrounding scars from any cause. The involvement is irregular as regards the poion of acinus involved as well as within the lung as a whole. During life, irregular emphysema is often asymptomatic and may be only an incidental autopsy finding. MIXED (UNCLASSIFIED) EMPHYSEMA. Quite often, the same lung may show more than one type of emphysema. It is usually due to more severe involvement resulting in loss of clearcut distinction between one type of emphysema and the other. Thus, the lungs of an elderly smoker at autopsy may show continuation of centriacinar emphysema in the upper lobes, panacinar in the lower lobes, and paraseptal emphysema in the subpleural region.