New concepts in the pathogenesis of sarcoidosis.

Introduction: The pathogenesis of sarcoidosis is not yet completely understood, although in recent years our knowledge has made considerable progress. Areas covered: This review aims to highlight the latest findings, identified from PubMed, EMBASE, and Web of Science, on the pathogenetic mechanisms of sarcoidosis, considering the studies on potential environmental antigens, genetic background and host immune responses. Particular emphasis has been on recent studies on antigens, as it now seems clear that it is not a single, but various antigens of microbial and non-microbial origin that share the ability to induce the series of immune-inflammatory events that lead to granuloma formation, activating host genetically influenced immune responses that involve innate and even more adaptive immunity. The dysregulation of Th17, Th17.1 cells and Tregs, and their role in the resolution and maintenance of granulomatous inflammation has been reported. Expert opinion: The considerable amount of data that has been accumulated on sarcoidosis pathogenesis will have to be carefully interpreted, particularly to discover which pathways lead to severe forms with organ damage. There is an urgent need for a panel of biomarkers indicating the involvement of the various pathways, to be used for better characterizing patient phenotypes and developing targeted therapies.