Update on genetics and pathogenesis of autoinflammatory diseases: the last 2 years

Abstract

Autoinflammatory diseases are a genetically heterogeneous group of rheumatologic diseases that are driven by abnormal activation of the innate immune system. Patients present with recurrent episodes of systemic inflammation and a spectrum of organ-specific comorbidities. These diseases are mediated by the overproduction of various inflammatory cytokines, such as IL-1, IL-18, IL-6, TNFα, and type I interferon. Treatments with biologic agents that inhibit these cytokines have been very efficient in most patients. During the past 2 years, remarkable progress has been made in the identification of disease-associated genes owing mostly to new technologies. Next generation sequencing technologies (NGS) have become instrumental in finding single-gene defects in undiagnosed patients with early onset symptoms. NGS has advanced the field of autoinflammation by identifying disease-causing genes that point to pathways not known to regulate cytokine signaling or inflammation. They include a protein that has a role in differentiation of myeloid cells, a ubiquitously expressed enzyme that catalyzes the addition of the CCA terminus to the 3-prime end of tRNA precursors, and an enzyme that catalyzes the oxidation of a broad range of substrates. Lastly, newly described mutations have informed a whole new dimension on genotype-phenotype relationships. Mutations in the same gene can give rise to a range of phenotypes with a common inflammatory component. This suggests greater than anticipated contributions by modifying alleles and environmental factors to disease expressivity.