The serum levels of some of the common genotypes are:

PiMM: 100% (normal)
PiMS: 80% of normal serum level of A1AT
PiSS: 60% of normal serum level of A1AT
PiMZ: 60% of normal serum level of A1AT
PiSZ: 40% of normal serum level of A1AT
PiZZ: 10-15% (severe alpha-1 antitrypsin deficiency)
PiZ is caused by a glutamate to lysine mutation at position 342 (366 in pre-processed form)
PiS is caused by a glutamate to valine mutation at position 264 (288 in pre-processed form)Other rarer forms have been described; in all, there are over 80 variants. Medical uses
Alpha-1 antitrypsin concentrates are prepared from the blood plasma of blood donors. The US Food and Drug Administration (FDA) has approved the use of four alpha-1 antitrypsin products derived from a human plasma: Prolastin, Zemaira, Glassia, and Aralast. These products for intravenous augmentation A1AT therapy can cost up to $100,000 per year per patient. They are administered intravenously at a dose of 60 mg/kg once a week; higher doses do not provided additional benefit although they can be used in anticipation of an interruption of weekly administration, such as for a vacation.Alpha1-proteinase inhibitor (Respreeza) was approved for medical use in the European Union in August 2015. It is indicated for maintenance treatment, to slow the progression of emphysema in adults with documented severe alpha1-proteinase inhibitor deficiency (e.g., genotypes PiZZ, PiZ (null), Pi (null, null), PiSZ). People are to be under optimal pharmacologic and non-pharmacologic treatment and show evidence of progressive lung disease (e.g.
Alpha-1 antitrypsin or α1-antitrypsin (A1AT, α1AT, A1A, or AAT) is a protein belonging to the serpin superfamily. It is encoded in humans by the SERPINA1 gene. A protease inhibitor, it is also known as alpha1–proteinase inhibitor (A1PI) or alpha1-antiproteinase (A1AP) because it inhibits various proteases (not just trypsin). In older biomedical literature it was sometimes called serum trypsin inhibitor (STI, dated terminology), because its capability as a trypsin inhibitor was a salient feature of its early study. As a type of enzyme inhibitor, it protects tissues from enzymes of inflammatory cells, especially neutrophil elastase, and has a reference range in blood of 0.9–2.3 g/L (in the US the reference range is expressed as mg/dL or micromoles), but the concentration can rise manyfold upon acute inflammation.When the blood contains inadequate amounts of A1AT or functionally defective A1AT (such as in alpha-1 antitrypsin deficiency), neutrophil elastase is excessively free to break down elastin, degrading the elasticity of the lungs, which results in respiratory complications, such as chronic obstructive pulmonary disease, in adults. Normally, A1AT leaves its site of origin, the liver, and joins the systemic circulation; defective A1AT can fail to do so, building up in the liver, which results in cirrhosis in either adults or children. In addition to binding to neutrophil elastase released by inflammatory cells, A1AT also binds to elastase localized on the cell surface in which case elastase does not act as an enzyme, but instead acts to signal cells to undergo locomotion.