Summary
The adult bronchiolitis obliterans with obstructive ventilatory defect is characterized by inflammatory and fibrosing thickening of bronchiolar walls that reduces the diameter of the bronchioles and results in airflow obstruction. It can either follow an acute episode of known cause, develop in particular contexts with undetermined mechanism, or exceptionally occurs as an isolated disorder (idiopathic bronchiolitis). Inhaled toxic gases as NO2, or infections (although rarely in adults) can trigger the disease. Bronchiolitis obliterans can sometimes occur in systemic disorders such as rheumatoid arthritis where it seems to be induced by D-penicillamine. It is also a severe complication of lung and bone marrow tranplantation due to chronic rejection and graft vs. host disease, respectively. Idiopathic forms are thought to be very rare, although many of them may be wrongly diagnosed as usual chronic obstructive pulmonary disease. Signs and symptoms include initial exertion dyspnea often associated with cough and recurring bronchial infections (usually caused by progressive bronchectasis due to inflammation of the large bronchi). Spirometry provides evidence of an ongoing obstructive disease that is little or not reversible. Hypoxemia occurs late in the development of disease. Imaging yields little information, although a suggestive 'mosaic' aspect may be seen on CT scan. Diagnosis is established on pulmonary biopsy, which shows parietal bronchiolitis, usually with no sign of alveolar, inflammatory or fibrous disorder (fibrosis may completely destroy the bronchioles leaving only a fibrous scar). In some circumstances, such as after lung transplantation, the combination of radioclinical and functional data may suffice to secure the diagnosis without biopsy. Corticosteroids and immunosuppressors may stabilize or improve patients, particularly when cellular inflammation is still important. Outcome is usually respiratory failure that may require lung transplantation. *Author: Pr. J.F. Cordier (April 2002)*
