06. ICD - 9 714 OMIM 180300 DiseasesDB 11506 MedlinePlus 000431 eMedicine med/2024 emerg/48 pmr/124 MeSH D001172 Rheumatoid arthritis ( RA ) is a chronic, systemic inflammatory disorder that may affect many tissues and organs, but principally attacks synovial joints . The process produces an inflammatory response of the synovium (synovitis)