Although the layman generally thinks of emphysema as a single disease, there are actually three distinct described morphological types of emphysema.
Emphysema, generally, is caused by the destruction of the alveoli, or the air sacs in the lungs that act as the gas-blood barrier, allowing inhaled oxygen to enter the bloodstream from the lungs and waste carbon dioxide to be pass from the bloodstream to the lungs to be exhaled. Symptoms usually present relatively mildly, but gradually worsen, and include shortness of breath, a feeling of tightness across the chest, weight loss and anorexia, loss of breath after only moderate physical activity, loss of breath after bending over, wheezing, chronic and acute fatigue, and a productive cough. The productive cough, often worst in the mornings and generally the first symptom to appear, commonly shows up when a patient is somewhere between forty and fifty years old. It can take up to another decade for other symptoms to appear.
Centriacinar emphysema, or centrilobular emphysema, is characterized by damage that begins in the last branch of the bronchioles before the alveoli and then spreads peripherally to the alveoli. Most of the damage is usually contained to the upper half of the lungs. This type of emphysema is particularly characteristic of the damage caused by cigarette smoking.
Panacinar emphysema is characterized by the uniform destruction of the alveoli. It is generally contained to the bottom half of the lungs. It is most often caused by homozygous alpha1-antitrypsin (AAT) deficiency, a genetic deficiency of a protein that supports the elasticity of lung structures. It can also present concurrently with centriacinar emphysema in smokers.
Paraseptal emphysema, or distal acinar emphysema, is characterized by the destruction of the distal airways structures, the alveolar ducts, the alveolar sacs, and the pleura, or the lining that protects and cushions the lungs. Oxygen and carbon dioxide exchange often continues relatively unaffected, but the condition can cause a spontaneous pneumothorax, or collapse of a lung, because of the buildup of pressure outside the lung. Giant bullae or air pockets trapped in damaged lung tissue can sometimes also cause severe compression of surrounding lung tissue
Quote: “Most of cases of COPD are the result of exposure to noxious stimuli, most often cigarette smoke. The normal inflammatory response is amplified in persons prone to COPD development.1 Genetics are believed to play a role in this response because not all smokers develop the disease“.
Source:Berj George Demirjian, MD, Fellow, Division of Pulmonary/Critical Care Medicine, Cedars-Sinai Medical Center
eMedicine from WebMD
Quote: “These findings suggest that squamous carcinoma may be related to the pathologic process of emphysema in addition to the direct carcinogenic effect of smoking. In contrast, small cell carcinoma is associated quantitatively and temporally with smoking history. Any association with emphysema likely represents confounding.“
Source: Benjamin Smith, MD; McGill University, Montreal, QC, Canada
Chest. 2010; 138:248A
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