To assess the pathological changes in the lungs and liver of 42 individuals who died while enrolled in the Registry of Individuals with Severe Deficiency of Alpha-1 Antitrypsin (AAT), all available histopathologic surgical or postmortem-derived specimens were reviewed by the pathologist member of the Death Review Committee. The underlying cause of death was emphysema in 34 patients and cirrhosis in 2 patients. Slides of lung were graded for emphysema, and liver specimens were graded for fibrosis, using respective pictorial scoring systems. Correlations between the degree of pathological abnormality and clinical features were evaluated. All lungs exhibited severe panacinar emphysema (mean emphysema score, 7.9 +/- 1.06 [standard deviation], where 10 represents the greatest severity) with a lower lobe predominance. Centriacinar emphysema was minimal. No correlation was found between the pathological severity of emphysema and pulmonary function measurements, and no significant correlation was found between the degree of emphysema and the degree of hepatic fibrosis. Mildly increased bronchial gland-to-wall ratio accompanied mild inflammation and goblet cell hyperplasia. There were minimal changes in small airways. Dilatation of membranous bronchioles was a frequent finding; however, bronchiectasis of larger airways was a minor feature in only 6 patients (15%). Airway morphological features did not correlate with the clinical presence of chronic bronchitis or asthma. Although the lack of correlation between liver and lung pathological changes may reflect different pathogenetic mechanisms of liver disease and lung disease, the lack of correlation between emphysema grade and lung function likely reflects the skewed sample in a series of patients with advanced lung disease.