The DNA methylation Profile of Undifferentiated Arthritis Patients Anticipates their Subsequent Differentiation to Rheumatoid Arthritis

Undifferentiated arthritis (UA) is the term used to cover all the cases of arthritis that do not fit a specific diagnosis. A high proportion of UA patients can progress to rheumatoid arthritis (RA) or a different definite rheumatic disease, while others undergo spontaneous remission. In this study, we performed DNA methylation profiling of a UA cohort, in which progression into RA occurs for a significant proportion of the patients. Genome wide DNA methylation profiles were analyzed in peripheral blood mononuclear cells (PBMCs) from patients with undifferentiated arthritis (UA) in which, after one year of follow-up, a definite arthritis developed (rheumatoid arthritis (RA), psoriatic arthritis (PsA), osteoarthritis (OA), spondyloarthropathy (SpA) and reactive arthritis (ReA)). Additional PBMC samples from definite RA patients were also analyzed.