[Nosology of inflammatory diseases: lessons learned from the auto-inflammatory syndromes--a focus on skin manifestations].

Auto-inflammatory diseases were first described more than 10 years ago as inherited disorders, characterized by recurrent flares of inflammation due to an abnormality in the innate immune system. The understanding of the underlying pathogenic mechanisms of these disorders, and especially the fact that they are mediated by IL-1 secretion by stimulated monocytes/macrophages, facilitated significant progress in patient management. IL-1 inhibitors are especially effective, and indeed, a brief and complete response to IL-1 inhibition is probably one of the best signs of auto-inflammation. Cutaneous manifestations are frequent in the monogenic auto-inflammatory syndromes, and a careful analysis of those findings reveals that they are almost always the consequence of neutrophilic skin infiltration. The neutrophilic dermatoses are, therefore, the cutaneous manifestations of those disorders. Even when the neutrophilic dermatoses occur outside the setting of genetically determined auto-inflammatory disorders, they probably also result from auto-inflammatory mechanisms. The distinction between auto-inflammation and autoimmunity is essential for the proper treatment of the patients. Auto-inflammation will almost always respond to IL-1 inhibition, while immunospressors will not be beneficial. The aim of the current paper is to review these two sub-groups of inflammatory diseases, focusing on their cutaneous manifestations, and highlighting the connection between these syndromes and inflammation in general.