Explosion of autoimmune diseases and the mosaic of old and novel factors.

In recent decades, an enormous effort has been made to elucidate the pathogenesis of autoimmune and autoinflammatory diseases. Autoimmunity is a multifactorial process in which genetic, immunological, environmental and hormonal factors play in concert, together representing what was termed years ago the 'mosaic of autoimmunity'. To date, more than 80 systemic and organ-specific autoimmune diseases have been defined, and their cumulative burden is substantial, both medically and financially. Furthermore, the burden of autoimmune and autoinflammatory diseases is rising, making these diseases a ubiquitous global phenomenon that is predicted to further increase in the coming decades. In this issue of the journal, additional aspects of autoimmunity are detailed. Immune dysregulation and loss of self-tolerance are the cornerstones of autoimmunity.