COPD and Bronchiectasis

Chronic obstructive pulmonary disease (COPD) and bronchiectasis are two of the most common chronic inflammatory diseases of the airways [1, 2]. They share a similar clinical-functional picture, and this often leads to mistaken diagnoses [3]; they also share a similar inflammatory profile, dominated by neutrophils [4]. Nevertheless, the two diseases are fundamentally different in terms of their prognosis and therapeutic management [5, 6]. Over and above the fact that the two diseases could appear by chance in a single patient, the relationship between COPD and bronchiectasis is a complex one from both angles. On the one hand, the prevalence of bronchiectasis seems to increase in COPD patients (particularly in the latter’s most severe forms) [7, 8]; on the other, an increasing presence of COPD can be seen in the etiological tables for bronchiectasis [9, 10]. So far, however, no study has demonstrated any causal relationship between the two diseases. Furthermore, it has been noted that patients with alpha-1 antitrypsin deficiency (a rare form of COPD characterized by the presence of panacinar emphysema, typically found in smokers), presents a high prevalence of bronchiectasis [11, 12]. Nevertheless, bronchiectasis of an unknown cause in COPD patients seems to constitute a special group or clinical phenotype with a more severe clinical-functional picture, a greater number of exacerbations, and even, according to some authors, a poorer prognosis [13–15]. One critically important aspect is the special management required by patients with both COPD and bronchiectasis since, as reflected in the international guidelines for both diseases [5, 6], each must be treated individually (and the scientific evidence shows that the same treatment can have markedly different effects on COPD and bronchiectasis). This chapter collates and discusses the literature to date on this complex relationship, in terms of epidemiology and the impact of bronchiectasis on patients with classical COPD, a predominance of emphysema, or an alpha-1 antitrypsin deficiency (α1-ATD). It also considers the possible therapeutic implications of this association, as well as hypotheses on a causal relationship between the two diseases and the most suitable approaches for future research aimed at expanding the scientific evidence on this subject.