bronchioles, are affected, while distal alveoli are spared. Thus, both emphysematous and normal air spaces exist within the same acinus and lobule (see
Fig.
13.5B ). The lesions are more common and severe in the upper lobes, particularly in the apical segments. In severe centriacinar emphysema, the distal acinus also becomes involved, and thus, the differentiation from panacinar emphysema becomes difficult. This type of emphysema is most common in cigarette smokers, often in association with chronic bronchitis.
• Panacinar (panlobular) emphysema. In panacinar (panlobular) emphysema, the acini are uniformly enlarged, from the level of the respiratory bronchiole to the terminal blind alveoli (see
Fig. 13.5C ). In contrast to centriacinar emphysema, panacinar emphysema occurs more commonly in the lower lung zones and is associated with α1-anti-trypsin deficiency.
• Distal acinar (paraseptal) emphysema. In this form of emphysema, the proximal portion of the acinus is normal but the distal part is primarily involved. The emphysema is more striking adjacent to the pleura, along the lobular connective tissue septa, and at the
Chronic injury (e.g., smoking)
Fig. 13.4 Schematicrepresentationofoverlapbetweenchronicobstructivelungdiseases.Small airway disease EMPHYSEMA Alveolar wall destruction Overinflation CHRONIC BRONCHITIS Productive cough Airway inflammation ASTHMA Reversible obstruction Bronchial hyperresponsiveness triggered by allergens, infection, etc.
margins of the lobules. It occurs adjacent to areas of fibrosis, scarring, or atelectasis and is usually more severe in the upper half of the lungs. The characteristic finding is the presence of multiple, contiguous, enlarged air spaces ranging in diameter from less than 0.5 mm to more than 2.0 cm, sometimes forming cystic structures that, with progressive enlargement, give rise to bullae. The cause of this type of emphysema is unknown; it comes to attention most often in young adults who present with spontaneous pneumothorax.
Fig. 13.5 Majorpatternsofemphysema.(A)Diagramofnormalstructureoftheacinus,thefundamentalunitofthelung.(B)Centriacinaremphysemawithdilationthatinitiallyaffectstherespiratorybronchioles.(C)Panacinaremphysemawithinitialdistentionofalltheperipheralstructures(i.e.,thealveolusandalveolarduct);thediseaselaterextendstoaffecttherespiratorybronchioles.
http://ebooksmedicine.net
Oxidative stress, Inflammatory increased cells, release of
Fig. 13.6 Pathogenesisofemphysema.Seetextfordetails.
• Irregular emphysema. Irregular emphysema, so named because the acinus is irregularly involved, is almost invariably associated with scarring, such as that resulting from healed inflammatory diseases. Although clinically asymptomatic, this may be the most common form of emphysema.
Inhaled cigarette smoke and other noxious particles cause lung damage and inflammation, which, particularly in patients with a genetic predisposition, result in parenchymal destruction (emphysema) and airway disease (bronchiolitis and chronic bronchitis). Factors that influence the development of emphysema include the following (
Fig. 13.6