PURPOSE: Bronchiectasis is increasingly recognized but the etiology is often unclear. In the 1990s, a rigorous investigation into the cause of bronchiectasis in a UK population determined an etiology in 47% of patients, most of which were postinfectious. The purpose of this study is to define the etiology of bronchiectasis in a U.S. based population.
METHODS: Patients with bronchiectasis were referred for evaluation over nine months. Bronchiectasis was confirmed by HRCT. Approval was granted by the Institutional Review Board. Clinical assessment was obtained by clinical questionnaire. Immune function was evaluated by measuring immunoglobulin (Ig) A, E, G, and M levels, IgG subsets, T cell subtypes, and, when indicated, titers to S. pneumonia, tetanus, and H. influenzae. Serologic autoantibodies and alpha-1-antitrypsin phenotype and level were measured. The results of HRCT, pulmonary function tests, and sputum cultures were recorded. Sinus CT and ciliary biopsy and CF gene testing was done when indicated.
RESULTS: 73 patients were evaluated. Data are complete for 64 patients. The mean (SD) age of the group was 66 (14) years. Patients were predominantly U.S. born (78%), female (68%), nonsmokers (66%) with mild reduction in lung function, mean FEV1 = 73% (22.3), and RV/TLC 49% (10.2). An etiology was determined in the majority of the patients (95%) and was most commonly related to an immune deficiency, low immunoglobulins (28%), malignancy (16%), or HIV (1.5%), or an autoimmune process (36%). Postinfectious bronchiectasis was found in only 1 patient (1.5%). Pseudomonas aeruginosa (n=34 isolates) and nontuberculous mycobacteria (n=23 isolates) were the most frequently identified organisms.
CONCLUSION: The etiology of bronchiectasis can be identified in a much higher percentage of patients than previously noted. The most common cause of bronchiectasis is immune dysregulation from either hypo- or hyperimmunity.
CLINICAL IMPLICATIONS: In a U.S. based population, systematic evaluation is likely to reveal an etiology and potential opportunity for therapy in the majority of patients with bronchiectasis.
DISCLOSURE: Pamela McShane, No Financial Disclosure Information; No Product/Research Disclosure Information