Pulmonary sarcoidosis

Sarcoidosis is a multisystemic disease of unknown aetiology characterized by the formation of immune granulomas in involved organs. It is a worldwide disease that mainly affects 25-40 years old people with a lifetime incidence rate of 0.85-2.4%. Multiple clinical phenotypes are observed according to presentation, involved organs, disease duration and severity. Sarcoidosis primarily affects the lungs and the lymphatic system. The prevailing pathogenic hypothesis is that various antigens could promote sarcoidosis in genetically susceptible hosts, both these factors modulating the incidence and the clinical phenotype of sarcoidosis. So far, environmental agents have been suspected, including possible mycobacteria and propionibacteria. Interferon-gamma, tumour necrosis factor (TNF)-alpha, interleukin (IL)-12 and IL-18 play a critical role in driving the Th1 commitment in the course of granulomatous process. Evolution of sarcoidosis is often marked by spontaneous resolution within 12-36 months, but can be severe because of chronic cases with pulmonary fibrosis or involving other organs, including heart, central nervous system and eyes. Mortality, ranging between 0.5 and 5%, is most often related to pulmonary fibrosis. Corticosteroids can reverse the granulomatous process, but are only suspensive, and their long-term benefit remains under question. Corticosteroids are recommended when sarcoidosis shows unfavourable clinical tolerance and evolution. Alternative and corticosteroid-sparing therapies are of increased interest in difficult cases, while targeted new drugs such as anti-TNF-alpha are still under investigation.