How should we approach classification of autoinflammatory diseases?

ABSTRACT

The notion of 'autoinflammatory' disease was introduced at the end of the 1990s, and, since then, this concept has rapidly evolved. As a result, multiple definitions of autoinflammatory disease, and classifications of conditions encompassed by these definitions, have been proposed; this succession highlights advances that have been made in understanding of the innate immune system, and especially the roles of IL-1ß and the inflammasome in autoinflammtory conditions. However, the definitions and classifications that have been suggested to date face a number of structure and content issues. We therefore propose another, more clinically-oriented, definition autoinflammatory diseases are diseases with clinical signs of inflammation, associated with elevated levels of acute-phase reactants, which are attributable to dysfunction of the innate immune system, genetically-determined or triggered by an endogenous factor. From this foundation, we propose a clinically-based classification of autoinflammatory diseases, and go on to discuss how immunological diseases as a whole, including autoimmune diseases, can be appropriately located within a continuum only if the classification process is multidimensional. For this purpose, we appeal to the philosophical concepts of family resemblance and signature.