SERPINA1 and pulmonary emphysema: It is because of these low circulating levels of AAT that patients with this condition are at a high risk of developing emphysema.30 The low level of AAT in ZZ individuals results in an imbalance of proteases and antiproteases in the AATD lung, resulting in unchecked levels of active serine proteases that damage alveolar tissue leading to lung disease.28,31