Alpha-1 antitrypsin (AAT) deficiency - what are the treatment options?

Abstract

Alpha-1 antitrypsin (AAT) deficiency is an under-recognized genetic condition that predisposes to liver disease and early-onset emphysema. Although AAT is mainly produced in the liver, its main function is to protect the lung against proteolytic damage from neutrophil elastase. The most common mutation responsible for severe AAT deficiency, the so-called Z variant, reduces serum levels by promoting polymerization of the molecule within the hepatocyte, thereby reducing secretion. Serum levels below the putative protective threshold level of 11 micromolar (μmol/L) increase the risk of emphysema. In addition to the usual treatments for emphysema, infusion of purified AAT from pooled human plasma represents a specific therapy for AAT deficiency and raises serum and epithelial lining fluid levels above the protective threshold. Substantial evidence supports the biochemical efficacy of this approach, particularly for the weekly infusion regimen. Definitive evidence of clinical efficacy is still needed, as the two available randomized controlled trials showed non-significant trends towards slowing rates of loss of lung density on lung computerized axial tomography. However, concordant results of prospective cohort studies suggest that augmentation therapy has efficacy in slowing the rate of decline of lung function in patients with moderate airflow obstruction and severe deficiency of AAT. Overall, augmentation therapy is well-tolerated and, despite its failure to satisfy criteria for cost-effectiveness, is recommended because it is the only currently available specific therapy for AAT deficiency.