According to this hypotesis, Araujo et al. showed an intriguing association between phenotype ZZ and the severity of bronchiectasis, independent of the presence of emphysema: within 110 patients with AATd, 26 were found to have bronchiectasis; in this group, mean value of AAT was 59.9 mg/dL; the ZZ phenotype was the most prevalent (42.3%); and there was a correlation between the severity of AATd and bronchiectasis, with a preponderance of the phenotype ZZ (100%) within the group with the most severe cases. This evidence concerns the gene SERPINA1 and bronchiectasis.