Alpha-1-antitrypsin (A1AT) deficiency is a common hereditary disorder characterized by a reduction of serum levels of A1AT, emphysema, and occasionally liver disease.
A1AT is produced in the liver and is normally released into the blood. A gene mutation sometimes produces an abnormal form of this protein which gets hung up in the liver and can enter the blood stream. This form (called the Z variant, or PiZ (protease inhibitor Z)) is the most common cause of A1AT deficiency. Another form PiS is more common but causes a less severe deficiency. Other variants also occur.
The type of emphysema produced with A1AT deficiency is usually the panacinar type, and most seriously affects the lower portions of the lungs. This is a diffuse type of emphysema. Cigarette smoking in those with normal A1AT most commonly affects the upper portions of the lung; this is usually called centrilobular emphysema. Treatment of emphysema is the same, no matter what the type is; except that the more diffuse emphysema of A1AT is sometimes too diffuse for successful LVRS (Volume Reduction Surgery).