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World J Rheumatol. Mar 12, 2013; 3(1): 3-5
Published online Mar 12, 2013. doi: 10.5499/wjr.v3.i1.3
What qualifies as rheumatoid arthritis?
Bruce Rothschild
Bruce Rothschild, Department of Medicine, Northeastern Ohio Medical University, Rootstown, OH 44272, United States
Bruce Rothschild, Biodiversity Institute, University of Kansas, Lawrence, KS 66045, United States
Author contributions: Rothschild B solely contributed to this paper.
Correspondence to: Bruce Rothschild, MD, FACR, Professor of Medicine, Biodiversity Institute, University of Kansas, Lawrence, KS 66006, United States. bmr@ku.edu
Telephone: +1-785-6151523 Fax: +1-785-5942691
Received: December 17, 2012
Revised: January 13, 2013
Accepted: January 23, 2013
Published online: March 12, 2013

Expansion of diagnostic criteria for rheumatoid arthritis and deletion of exceptions increases sensitivity, but at the expense of specificity. Two decades later, modification of criteria included the caveat: “absence of an alternative diagnosis that better explains the synovitis.” That puts great faith in the diagnostic skills of the evaluating individual and their perspectives of disease. The major confounding factor appears to be spondyloarthropathy, which shares some characteristics with rheumatoid arthritis. Recognition of the latter on the basis of marginally distributed and symmetrical polyarticular erosions, in absence of axial (odontoid disease excepted) involvement requires modification to avoid failure to recognize a different disease, spondyloarthropathy. Skeletal distribution, pure expression of disease in natural animal models and biomechanical studies clearly rule out peripheral joint fusion (at least in the absence of corticosteroid therapy) as a manifestation of rheumatoid arthritis. Further, such studies identity predominant wrist and ankle involvement as characteristic of a different disease, spondyloarthropathy. It is important to separate the two diagnostic groups for epidemiologic study and for clinical diagnosis. They certainly differ in their pathophysiology.

Keywords: Rheumatoid arthritis, Spondyloarthropathy, Ankylosis, Accelerometry, Animal models