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Genetics of Alpha-1 Antitrypsin Deficiency

written by: R. Elizabeth C. Kitchen•edited by: lrohner•updated: 10/31/2010

Are you looking for information about the genetics of alpha-1 antitrypsin deficiency? If so, read on to learn more about the genetics and other information.

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    Alpha-1 antitrypsin deficiency, also referred to as AAT deficiency, is a genetic disorder in which the protein responsible for protecting the liver and lungs from becoming damaged is deficient. The liver is responsible for making this protein and when it does not produce sufficient amounts, this condition occurs.

    The genetics of alpha-1 antitrypsin deficiency revolves around inadequate amounts of AAT being present in the lungs, liver and blood. In those of European ancestry, about one in 1,500 to 3,500 people are affected. Many people with this condition are likely undiagnosed, according to Genetics Home Reference.

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    Patients who have this genetic disorder typically begin experiencing the initial signs of lung disease between 20 and 50 years of age. Understanding the genetics of alpha-1 antitrypsin deficiency involves knowing that this disorder is inherited, or passed down, in an autosomal codominant pattern.

    The SERPINA1 gene is involved with this disorder. When this gene is mutated AAT deficiency can result. The SERPINA1 gene is responsible for giving the necessary instructions for the creation of the alpha-1 antitrypsin protein. This protein helps in protecting the body from neutrophil elastase, a powerful enzyme. This enzyme fights infection and the white blood cells release it. However, if the alpha-1 antitrypsin protein is not tightly controlling the neutrophil elastase enzyme, this enzyme can attack normal tissues, specifically the tissues in the lungs.

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    This disorder may cause a variety of signs and symptoms. These include:

    • Shortness of breath without being exerted and when exerted
    • Symptoms of cirrhosis
    • Wheezing
    • Unintentional weight loss
    • Chronic obstructive pulmonary disease symptoms
    • Recurring respiratory infections
    • Rapid heartbeat when the patient stands up
    • Fatigue

    If emphysema is present the patient may present with trouble breathing, barrel-shaped chest, and hacking cough. If cirrhosis is present the patient may present with swollen feet or legs, swollen abdomen, and jaundice.

    Though rare, panniculitis, a skin condition, may also occur. This condition is characterized by painful patches or lumps with hardened skin.

    Patients with this genetic disorder may also present with:

    • Emphysema before 45 years of age
    • Hepatitis or liver disease without any other cause
    • Emphysema without ever being exposed to toxins or smoking

    Possible complications include:

    • Emphysema
    • Liver failure or cirrhosis
    • Liver cancer
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    Diagnosing this disorder will begin with a physical exam. Patients may have a barrel-shaped chest, or decreased breath sounds and wheezing upon examination. Diagnostic testing may include:

    • Alpha-1 antitrypsin blood test
    • Chest x-ray
    • Genetic testing
    • Pulmonary function test
    • Arterial blood gases
    • Chest CT scan
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    Replacing AAT protein that is missing is how this disorder is treated. Every week the patient will have this protein administered intravenously. If cirrhosis and/or emphysema is present the patient will also be treated for these. All patients who smoke must quit smoking.

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    MedlinePlus. (2008). Alpha-1 Antitrypsin Deficiency. Retrieved on September 16, 2010 from MedlinePlus:

    Genetics Home Reference. (2009). Alpha-1 Antitrypsin Deficiency. Retrieved on September 16, 2010 from Genetics Home Reference: