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Undifferentiated early inflammatory arthritis in adults

Josef S Smolen, MD
Section Editor
Peter H Schur, MD
Deputy Editor
Paul L Romain, MD


In some patients with inflammatory arthritis, it is not possible to establish a specific diagnosis during the first several weeks to months following symptom onset, although such patients, with undifferentiated early inflammatory arthritis, require effective treatment for their condition to begin to alleviate the symptoms and functional impairment associated with active disease, ie, active inflammation of any one or more joints in terms of synovitis as manifested by joint swelling [1-6].

Inflammatory arthritis is characterized by an influx of inflammatory cells, such as monocytes/macrophages, lymphocytes, and granulocytes, from the blood stream into the synovial membrane or their accrual in the synovial fluid, and is frequently associated with hyperplasia of synovial fibroblasts. This inflammatory process causes pain, swelling (and in some instances redness) of the joint, frequently associated with reduced mobility and functional impairment; moreover, in some diseases damage to cartilage and bone can ensue, leading to joint destruction. Inflammatory arthritis contrasts from osteoarthritis, which is regarded a degenerative joint disease, or mere arthralgia which may have many causes. In many non-English speaking countries, the term “inflammatory arthritis” is regarded as pleonastic, since the term “arthritis” as an “-itis” already indicates inflammation, and other diseases, such as osteoarthritis, are named “arthrosis.” However, for the sake of this review and for clarity we will retain the term.

The term ”undifferentiated arthritis” (UA) is used here to describe patients with undifferentiated early inflammatory arthritis, typically between six weeks and a year in duration, although a diagnosis can often be determined within three months and only infrequently requires as long as a year to become evident. Many such patients will eventually be diagnosed with rheumatoid arthritis (RA) after further evolution of the symptoms and findings.

Inflammation is generally reversible, while joint destruction is not; and early and appropriate treatment before a definitive diagnosis can be established may prevent disease persistence, joint damage, and the disability and disease comorbidities associated with the ongoing disease process [1-9]. Early treatment, even without a definitive diagnosis, may also be of benefit because the immunopathologic events mediating the disease process, as in RA, may evolve and differ in later stages from the changes in early disease [10]. Cartilage and bone injury, including erosions, may occur early in the disease course, be irreversible once present, and be associated in RA with greater disease severity, possibly by several mechanisms [11,12]. Whether there is an early “window of opportunity” for inducing remission in RA and other inflammatory arthritides remains uncertain [13].

The evaluation and management of patients with UA will be presented here. The evaluation of patients with monoarticular and polyarticular pain; synovial fluid analysis; the diagnosis of septic arthritis and gout; and the diagnosis and differential diagnosis of RA, axial and peripheral spondyloarthritis (SpA) (including psoriatic arthritis [PsA]), and other specific forms of arthritis are described in detail separately:

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Literature review current through: Nov 2017. | This topic last updated: Nov 29, 2016.
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