[Etiological work-up for bronchectasia in adults]

Search for an etiology of bronchiectasis consists in identifying constitutional or acquired defense mechanisms of the respiratory mucosa. The question is timely because causes change. In developing countries, presumed sequelae of infection account for about 30% of the cases despite vaccination campaigns, control of endemic tuberculosis, and widespread use of antibiotics. Genetic diseases account for 20% of the causes when identified by high-performance prospective diagnostic tests (CFTR mutation). Computed tomography enables the identification of frequent associations between bronchiectasis and rheumatoid disease or ulcerative colitis. Recent diseases such as HIV infection or GVHD can also lead to bronchiectasis. Nevertheless, the cause remains unknown in 30-50% of patients. After a detailed analysis of the clinical presentation and diagnostic criteria specific for each etiology, we propose a two-phase diagnostic procedure. The first step, used for all patients (careful history taking, physical examination, imaging, bronchofibroscopy, limited blood tests) enables detecting localized bronchial obstacles and obvious etiologies (situs inversus of primary ciliary dyskinesia, known systemic disease, HIV...). If the first step is negative, the second phase is oriented by the clinical context. Sequelae of infection (tuberculosis...) in older subjects or migrants, a genetic cause in younger subjects, particularly if there is a familial history and/or infertility, a systemic disease or allergic bronchopulmonary aspergillosis if there is an extra-respiratory context. This etiological search should help improve patient management and provide a better prognosis and prevention of bronchiectasis.