Alpha- l -Antitrypsin (AAT), is a chemical synthesized in the liver and circulating throughout via bloodstream. Also known as Alpha- l -Proteinase Inhibitor (A1 -PI), it is a member of the serpin or the serine protease inhibitor family. Its physiological target is elastase.
A normal individual inherits two AAT genes: one from each parent. Nevertheless, when individuals inherit two abnormal AAT genes they tend to show symptoms of alpha-1 deficiency. Some people inherit only one abnormal gene and they are called alpha-1 “carriers. ” Alpha-1 is therefore purely a genetically inherited condition.
According to the American Thoracic Society (2006), risk of major health problems in a person with one abnormal gene or a carrier may be lower as compared to a person with two abnormal genes (American Thoracic Society, 2006). WHO (2008) categorizes Alpha- l -Antitrypsin Deficiency (Alpha-1) as a genetic disorder that can cause liver and lung disease in adults and children. Alpha-1-antitrypsin (AAT) deficiency is associated with 85%-90% reduction in serum concentrations of AAT. This causes increased risk for liver and lung ailments such as cirrhosis, hepatocellular carcinoma and emphysema (Stoller, 2005; Primhak and Tanner, 2001).
In normal and healthy individuals, the primary role of AAT is to defend the connective tissue of lung against breakdown by a degradative enzyme called neutrophil elastase. In AAT deficient individuals, lack of AAT allows neutrophil elastase to destroy the connective tissue in the lungs (Stoller, 2005) and apart, in affected individuals, deficiency of blood levels below a level called “protective threshold” value makes them vulnerable to emphysema. This conditional may usually occur in prime of life, i. e. by age 40 even though there is absence of added risk factors such as cigarette smoking (Stoller, 1998).
Polymerization of a mutant AAT protein in the liver cells, along with abnormal accumulation of AAT in the liver ends in hepatocellular injury (Primhak and Tanner, 2001). It is believed that this abnormal accumulation of AAT within the liver cells is mainly due to a structural abnormality of the AAT protein. Normally, it is secreted from the hepatocyte and circulates through bloodstream, but in abnormal conditions it accumulates within liver cells leading to deficiency of AAT in the blood (Brantly et al. , 1988).
The mutant AAT molecules are usually retained in the endoplasmic reticulum of the hepatocyte and are also hepatotoxic . Teckman et al. (1996) reveals that these retained AAT appear to be periodic acid-Schiff (PAS)-positive, diastase-resistant eosinophilic inclusions in the periportal hepatocytes. Alpha-1 antitrypsin deficiency disorder occurs also in newborns. Primary symptoms in newborns are jaundice, swelling of the abdomen, and poor feeding. In late childhood or adulthood Alpha-1 disorder can be detected by symptoms such as poor appetite, fatigue, swelling of the abdomen and legs or abnormal liver tests.