Alpha-1 Anti-trypsin Deficiency (AATD) is a genetic disease with lung and liver disease presentations. Presentations are variable in the heterozygous population, the most predominant genotype being PiMZ. The purpose of this study in PiMZ heterozygous patients is to examine the density of the lung as measured by chest computed tomography (CT) and determine if existing emphysema predicts changes in the rate of subsequent emphysema or changes in CT, serum or plasma biomarkers of interest. The overarching goal is to develop biomarkers pertinent to the PiMZ patient that can be used in interventional trials since lung function changes do not typically inform disease progression in AATD.