Analysis of DNA methylation patterns in early and longstanding rheumatoid arthritis. (A) Hierarchical clustering of longstanding RA, (LRA), early RA (ERA), juvenile idiopathic arthritis (JIA) and osteoarthritis (OA) based on differentially methylated loci. (B) Analysis of the first three principal components of longstanding RA, (LRA), early RA (ERA), juvenile idiopathic arthritis (JIA) and osteoarthritis (OA) based on differentially methylated loci. Note that the inflammatory arthritis samples mainly cluster together, and that ERA segregates from JIA.