[Obstructive bronchiolitis].

The term "obstructive bronchiolitis" used in this review covers different clinicopathological aspects. On the one hand, it refers to "small airways disease", where bronchiolar narrowings are widespread, secondary to post inflammatory fibrotic changes linked to tobacco smoke or fibrogenic dust inhalation. These obstructive changes at the level of small airways are responsible for a fixed airflow limitation. The specificity and sensibility of functional tests designed for early detection of such an obstruction (the frequency dependence of compliance, the nitrogen slope and the density dependence of the flow-volume curve) are still controversial. On the other hand, the entity covers a disease described at the beginning of the century under the name "bronchiolitis obliterans". It usually appears as a consequence of various causes: viral infection, toxins acting either inhalation or by systemic route, immunological mechanisms as in connective tissue diseases or in graft versus host reactions. A special emphasis is put on idiopathic bronchiolitis obliterans associated with organizing pneumonia. Some clinicopathologic correlations are of basic interest in relation to etiological factors: bronchiolitis obliterans due to viral infection in children involving mainly membranous bronchioles; by contrast, bronchiolitis obliterans related to other causes seems to extend further down from the terminal bronchioles to the respiratory bronchioles. Lymphoid bronchiolitis appears non specific and is mostly observed in association with systemic connective tissue diseases, such as rheumatoid arthritis.