Background: Previous studies of patients with bronchiectasis have found that the cause is idiopathic in the majority of cases, but these studies were done in homogeneous populations. We hypothesized that the etiology of bronchiectasis can be determined in a higher percentage of patients in a diverse US population and will differ significantly based on ethnicity.
Methods: One hundred twelve patients with bronchiectasis confirmed by chest CT scan entered the study. Data from 106 patients were available for full evaluation. Clinical questionnaire, pulmonary function tests, sputum microbiology, laboratory data, and immune function testing were done. Results were analyzed by ethnicity and etiology.
Results: Patients were 61.6% European American (EA), 26.8% African American (AA), 8.9% Hispanic American (HA), and 2.7% Asian American. A cause of bronchiectasis was determined in 93.3% of patients. In 63.2% of patients, bronchiectasis was caused by immune dysregulation, including deficiency (n = 18 [17%]), autoimmune disease (n = 33 [31.1%]), hematologic malignancy (n = 15 [14.2%]), and allergic bronchopulmonary aspergillosis (n = 1 [0.9%]). Rheumatoid arthritis was the cause of bronchiectasis in 28.6% of AA patients vs 6.2% of EA patients (P < .05). Hematologic malignancy was the etiology in 20.0% of the EA patients vs none of the AA patients (P = .02). A significantly higher percentage of HA patients had Pseudomonas aeruginosa in their sputum compared with AA and EA patients (P = .01).
Conclusions: The etiology of bronchiectasis can be determined in the majority of patients in a heterogeneous US population and is most often due to immune dysregulation. Rheumatoid arthritis is more likely in AA patients than EA patients. HA patients are more likely to have P aeruginosa in their sputum.