Still's disease and the mitochondrion: the other face of an old friend?

Although Still's disease has been first described more than one century ago, it still appears as an orphan entity, which should be separated from the other auto-inflammatory diseases (AID). The main reason to individualize Still's disease among the AID is the absence of any genetic predisposition. Recently, the human mitochondria have been clearly implicated in the systemic inflammation that is observed during the innate immune response. After various types of cellular injuries, including infections, the release of "Damage-Associated Molecular Patterns" (DAMPs) from mitochondria can recruit circulating polymorphonuclear neutrophils (PMNs), monocytes and macrophages, along with the activation of NLRP3 inflammasome. Flares of Still's disease usually mimic systemic bacterial infections, with high levels of PMNs, but no evidence of circulating bacteria. Ubiquitous and usually benign viruses, such as human herpes virus 6 (HHV-6), appear capable of inducing mitochondrial damages. Such a phenomenon could in turn initiate the flares of Still's disease, thereafter persisting as an inappropriate and self-perpetuating reaction to an endogenous bacterial vestige, the mitochondrion itself.