[Autoinflammatory diseases]

The monogenic autoinflammatory diseases are rare, genetic disorders resulting in constitutive innate immune defects leading to excessive response to danger signals, spontaneous activation of inflammatory mediators or loss of inhibitory regulators. During the past 15 years, a growing number of monogenic inflammatory diseases have been described and their respective responsible genes identified. The proteins encoded by these genes are involved in the regulatory pathways of inflammation and are mostly expressed in cells of the innate immune system. Although a group of patients exhibit episodic systemic inflammation (periodic fevers), these disorders are mediated by continuous overproduction and release of pro-inflammatory mediators, notably IL-1β, and are best considered as autoinflammatory diseases rather than periodic fevers. The most common autoinflammatory diseases are familial Mediterranean fever (FMF), TNF receptor-associated periodic syndrome (TRAPS), mevalonate kinase deficiency/hyperimmunoglobulin D syndrome (MKD/HIDS) and the cryopyrin-associated periodic syndromes (CAPS). Clinical features often include fever, cutaneous rash, serosal involvement and acute phase reactants. Autoantibodies are usually absent but may accompany certain syndromes. Diagnosis remains clinical and is based on the different phenotypic features. Genetic diagnosis is of utmost importance, but must be performed judiciously and interpreted cautiously. Treatment with biologic agents that block proinflammatory cytokines, particularly IL-1, has proved to be dramatically effective in many patients. Still, in many cases of autoinflammation no genetic abnormalities are detected and treatment remains suboptimal, raising the question of novel pathogenic mutations in unexplored genes and pathways.