An integrated approach in the diagnosis of smoking-related interstitial lung diseases

Cigarette smoke consists of several chemical compounds with a variety of effects in many organs. In the lung, apart being the main cause of chronic obstructive pulmonary disease, carcinoma and idiopathic spontaneous pneumothorax, tobacco smoke is associated with interstitial lung diseases (ILDs), including respiratory bronchiolitis-associated ILD (RB-ILD), desquamative interstitial pneumonia (DIP), pulmonary Langerhans' cell histiocytosis (PLCH), idiopathic pulmonary fibrosis, acute eosinophilic pneumonia, ILD in rheumatoid arthritis and pulmonary haemorrhage in Goodpasture syndrome. This review will focus on the diseases with a stronger epidemiological association with tobacco smoke, namely RB-ILD, DIP and PLCH. Although the exact pathogenetic evidence linking smoking with these disorders is still not completely understood, there is growing evidence that tobacco smoke targets the terminal or respiratory bronchioles in these diseases, and the differences are reflective of the degree of severity of small airway and parenchymal reaction to the smoke exposure. Despite considerable clinical, radiological and histological overlap between RB-ILD, DIP and PLCH, it is useful to retain the separate classifications for prognostic and therapeutic implications.