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A Disease Often Misdiagnosed as Asthma
Emphysema is a lung disease that affects the walls of the alveoli, the small sacs in the lungs that exchange oxygen for carbon dioxide.
Emphysema causes the alveolar walls to lose their elasticity. This causes small pockets of dead air to remain in the lungs and makes it difficult to exhale air from the lungs. Most emphysema cases are caused by smoking, but about 3 percent of cases are caused by an inherited deficiency in a protein that normally protects the alveoli. This protein is alpha-1 antitrypsin (AAT). In emphysema caused by AAT deficiency, the small airways that lead to the alveoli are also damaged.
In the normal lung, chemicals called proteases are produced by the body's immune system to protect the lungs from infection. Two types of proteases are elastase and trypsin. If the concentration of proteases in the lungs is too great, they can attack healthy lung tissue, destroying elastin, a substance necessary to maintain the elasticity, or flexibility, of the alveoli. AAT neutralizes the proteases, the most important being elastase, and protects the elastin.
Produced in the liver
AAT is produced by the liver and released into the bloodstream.
In people with AAT deficiency, elastase attacks the walls of the alveoli, causing irreversible damage. If allowed to progress, lung tissue continues to be destroyed, and eventually fatal emphysema develops.
The first signs of AAT deficiency often appear between the ages of 20 and 40. The first symptoms are usually shortness of breath, wheezing following activity, and a decreased ability to exercise.
There is a key difference in this type of emphysema versus the common emphysema that many smokers battle. The AAT deficiency emphysema is found throughout the lungs. The smoker's emphysema is found in the central airway of the lungs. As the disease becomes severe, both types of emphysema look very much the same. Both have low levels of oxygen and carbon dioxide retention.
Mistaken for asthma
If a patient with chronic obstructive airways disease responds well to bronchodilators, health care providers say they have an "asthmatic component. Patients with AAT deficiency-related emphysema respond to bronchodilators, and they are often relatively young when they see a doctor about their symptoms, so they are often diagnosed with asthma.
Diagnosis of AAT deficiency is suspected when emphysema develops at a young age and in a person with a family history of lung disease at a young age. A simple breathing test that measures how forcefully a person exhales can help make the diagnosis. Testing for AAT deficiency includes measuring the amount of AAT in the blood and testing for the type of AAT genes.
Once AAT deficiency is diagnosed, treatment will require weekly intravenous infusions of the proteins, which come from human plasma donors.
Replacement therapy is not entirely effective in all cases. For those people, lung transplants offer hope. Approximately one fourth of all lung transplants are alpha-1 adults.
Patients also go through pulmonary rehabilitation. With pulmonary rehabilitation, they will learn different techniques of clearing sputum, the proper use of medications, and how to increase their exercise for more efficient use of oxygen.
The Z gene
In the most common type of alpha-1 antitrypsin deficiency, a person inherits one Z gene from each parent. In the United States there are an estimated 100,000 people with the alpha-1 antitrypsin deficiency ZZ gene expression.
Online ResourcesGenetics Home Reference http://ghr.nlm.nih.gov/condition/alpha-1-antitrypsin-deficiency
The Alpha-1 International Registry http://www.aatregistry.org/aatdetailed.html
American Association for Clinical Chemistry http://www.labtestsonline.org/understanding/analytes/alpha1_antitrypsin/test.html
American Lung Association http://www.lungusa.org/lung-disease/copd/
National Center for Biotechnology Information http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001153/
National Heart, Lung and Blood Institute http://www.nhlbi.nih.gov/health/dci/diseases/copd/copd_whatis.html