Alpha-1 Antitrypsin Deficiency-Associated Chronic Obstructive Pulmonary Disease.

Alpha-1 antitrypsin deficiency (AATD) is a genetic disorder characterized by reduced circulating levels and/or impaired function of alpha-1 antitrypsin (AAT), a key serine protease inhibitor, in which loss of effective antiprotease protection results in unchecked neutrophil elastase activity and progressive lung tissue destruction. Although AATD accounts for approximately 1% of chronic obstructive pulmonary disease (COPD) cases and up to 2% of emphysema, AATD-related COPD remains largely underdiagnosed, despite guideline recommendations for systematic evaluation in patients with COPD, particularly in high-risk clinical settings. Pathologically, AATD-related COPD is not limited to the typical early-onset, lower-lobe-predominant emphysema, also including upper-lobe or mixed emphysema patterns, airway-predominant disease, small airways dysfunction, and bronchiectasis. Clinically, AATD-related COPD is distinguished from smoking-related COPD by its earlier onset, physiological impairment that is often disproportionate to smoking exposure, and its potential presence of certain extrapulmonary manifestations. Diagnosis and monitoring are also challenged by the frequent discordance between airflow limitation and gas transfer impairment, as well as the early involvement of small airways, limiting reliance on spirometry alone. A multimodal assessment incorporating more sensitive functional techniques and CT densitometry may provide a more precise evaluation of disease burden, progression, and prognosis. Management generally follows standard COPD principles, with intravenous AAT augmentation therapy remaining currently the only established disease-modifying therapy for selected patients with severe deficiency. The advent of new pharmacological and gene-based therapies emphasizes the importance of developing personalized management strategies that integrate genotype and longitudinal disease behavior. This narrative review summarizes current evidence on AATD-associated COPD, focusing on its genetic basis and pathophysiological features, clinical and functional heterogeneity, current and emerging diagnostic and monitoring approaches, and disease-specific management considerations.