Epigenetics for Clinicians from the Perspective of Pediatric Rheumatic Diseases

Epigenetics is the study of inherited phenotype changes that do not involve in alteration of DNA sequence. Epigenetic regulation can be examined under three main headings and study methodologies for all three will be discussed: DNA methylation is the addition of a methyl (CH₃) group to DNA, histone modifications is a covalent post-translational modification of histones and non-coding RNAs are a group of functional RNA molecules that is copied from DNA but not converted into proteins. Epigenetic changes are being increasingly studied in the pathogenesis of most diseases including autoimmune and autoinflammatory diseases to shed light on the different phenotypes and disease courses. We have aimed to review the basic concepts in epigenetic studies and summarize the data for epigenetics in autoimmune and autoinflammatory rheumatic diseases.

Recent studies have assessed DNA hypomethylation in interferon-regulated genes in autoimmune diseases and in inflammatory pathways in systemic autoinflammatory diseases (SAIDs). Abnormal histone acetylation and methylation have been shown to be important in autoimmune diseases which was proven via effective targeted treatment trials against these pathways in mice models. miRNAs have an important role in the pathogenesis, and also, they can be used as diagnostic biomarkers in SAIDs (i.e., FMF, Behcet's disease) together with autoimmune diseases. Although the number of studies has increased over the years in parallel with the increase of interest in this field, we await further studies to improve the understanding and management of pediatric rheumatic diseases. Epigenetic studies in pediatric rheumatic diseases have enabled us to gain new information about disease pathogenesis, clinical heterogeneity, and prognosis. Further studies will help us define new diagnostic, prognostic, and therapeutic goals for rheumatic diseases.