Alpha-1 Antitrypsin Deficiency Beyond COPD and Emphysema: A Narrative Review

Background/Objectives: Alpha-1 antitrypsin deficiency (AATD) is a genetic disorder classically associated with emphysema and COPD. However, emerging evidence indicates that its clinical spectrum extends to airway-predominant diseases such as bronchiectasis and asthma, where protease-antiprotease imbalance and neutrophilic inflammation may drive tissue injury. This narrative review aims to synthesize current evidence on the relationship between AATD and airway diseases beyond emphysema, focusing on epidemiological patterns, underlying mechanisms, diagnostic strategies, and therapeutic implications. Methods: A narrative synthesis of the literature was performed, integrating data from registries, with observational and translational studies addressing the prevalence, pathobiology, and therapeutic implications of AATD in bronchiectasis, asthma, and severe asthma. Epidemiologic and mechanistic insights were analyzed to identify overlapping pathways and evidence gaps. Results: Evidence supports a non-negligible prevalence of bronchiectasis and asthma among AATD individuals, particularly in severe or heterozygous genotypes. Neutrophil elastase overactivity, impaired mucociliary clearance, and chronic neutrophilic inflammation emerge as shared mechanisms promoting bronchial remodeling and airflow limitation. In asthma, AATD appears linked to T2-low, steroid-resistant phenotypes and persistent obstruction, whereas in severe asthma cohorts, up to 20% may carry non-PiMM SERPINA 1 variants. No randomized trials have evaluated augmentation therapy and standardized screening algorithms are lacking. Conclusions: AATD represents a systemic disorder with clinically relevant airway manifestations beyond COPD and emphysema. Targeted testing should be considered in patients with idiopathic bronchiectasis or severe asthma. Future genotype-stratified, prospective studies are required to clarify causality, define biomarkers of disease activity, and evaluate the potential role of anti-protease-based therapeutic strategies.