Emphysema panlobular

Parenchymal changes affect the gas-exchanging units of the lungs (alveoli and pulmonary capillaries). Smoking-related disease most commonly results in centrilobular emphysema that primarily affects respiratory bronchioles. Panlobular emphysema is seen in AAT deficiency and extends to the alveolar ducts and sacs. 

In 42 solvent inhalers aged 11-31, residual volumes were significantly higher than in 20 controls aged 10-26 lung tissue obtained at autopsy from three inhalers contained microscopic abnormalities similar to those seen in experimental panlobular emphysema (10). 

Materials such as soybeans, lima beans, and egg whites contain natural TRY inhibitors—small polypeptides such as tti-antitrypsin (a-l-protease inhibitor) and a2-macroglob-uUn— that combine irreversibly with TRY and inactivate it by blocldng the active center. Similar nondialyzable TRY inhibitors are present in pancreatic juice, serum, and urine. These inhibitors protect plasma and other proteins against hydrolysis by TRY and other proteases if for some reason any appreciable quantity of the enzyme enters the vascular system. The absence of ai-antitrypsin is associated with an increased tendency toward panlobular emphysema in early hfe this example illustrates the effects of uninhibited proteases on organ function. 

Morphologically, emphysema is associated with a destruction of the alveolar septum, which results in a dilation and consequent enlargement of the alveolar spaces (Fig. 19). This is apparently caused by a breakdown of the interstitial connective tissue proteins (primarily elastin) that provide the major structural framework of the lung parenchyma. Two types of emphysema have been defined on the basis of the types of destruction of the alveolar septa observed and the type of dilation of the terminal respiratory unit (the acini) that is observed. A typical acinus branches from a terminal bronchiole and consists of the respiratory bronchioles that have alveolated walls and lead to the alveolar ducts and ultimately to the alveolar sacs (see Fig. 3). In centrilobular (or centriacinar) emphysema, the sites of degradation and dilation are limited to the region of the terminal and respiratory bronchioles. In panlobular (or panacinar) emphysema, the entire acinus (including the alveolar ducts and sacs) is more uniformly affected. 

Fig. 19. Pathological destruction of the alveolar structure (a) normal acinus, (b) cen-trilobular, and (c) panlobular emphysema.

Homozygous or heterozygous tti-antitrypsin deficiency offers a proteolytic mechanism and possible genetic basis for some cases of panlobular emphysema in miners (Falk and Briscoe 1970). The homozygous deficiency, which is known to be associated with emphysema, has been identified in 1 -10 % of various groups of patients (Briscoe et al. 1966, Kueppers et al. 1969, Lieberman 1969). 

The most important differential diagnoses for LAM are Langerhans cell histiocytosis, idiopathic pulmonary fibrosis, and panlobular emphysema. In contrast to LAM, in Langerhans cell histiocytosis, the costophrenic sulci are usually spared, the cysts can be thick-waUed and irregularly outlined, and nodules are predominant in the early stage of disease. Idiopathic pulmonary fibrosis shows a volume loss in contrast to LAM, and the honeycomb cysts are predominantly located in the lower lobes and subpleural (Bonelli et al. 1998). Panlobular emphysema is associated with alpha-1-antiprotease deficiency. The most distinct feature of emphysema is the absence of defined walls in the areas of low attenuation, whereas cysts in LAM almost invariably present with walls (Johnson 1999). 

Host factors. Genetic factors seem to influence the development of COPD (Molfino 2004). The most important is the Z-deficiency type of cii-antitrypsin, with increased risk of panlobular emphysema. Other gene factors might have an association with COPD, but data are premature. Bronchial hyperreactivity and disturbed growth of the lungs are associated with the disease. 

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