Two distinguishing features of long-standing RA are “swan neck” deformities and boutonniere deformities of the fingers (Figure 1).3 Swan neck deformities develop with hyperextension of the PIP joint and flexion of the distal interphalangeal (DIP) joint, whereas boutonniere deformities develop with flexion of the PIP joint and hyperextension of the DIP joint.12 A bowstring sign, which is the presence of prominent and tight tendons on the dorsum side of the hand, may also be evident on physical examination.
The wrist is the arm joint that is most commonly affected by RA. Difficulty bending the wrist backward is an early indicator of the disease, and movement requiring manipulation of the wrist is often arduous for patients with RA. Swelling of the elbow joint is also seen in RA; this can cause a tingling sensation running up the arm as a result of compression of the ulnar nerve. A limited range of motion in the shoulder may be noted on physical examination in the later stages of RA.
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Swan neck deformities in the fingers of an elderly woman with rheumatoid arthritis.
In the lower extremities, the bases of the toes are commonly affected at the onset of RA. Having a patient stand on his or her toes will elicit pain; moreover, the plantar surface of the foot may appear swollen and erythematous. Swelling and difficulty flexing the knee may also be evident on examination. Baker’s cysts are frequently observed in patients with RA. In progressive and late cases, RA may involve the hips, causing walking to be both painful and difficult.
Although not extremely common, involvement of the cervical spine may cause inflammation between the shoulders and base of the head, resulting in a painful and stiff neck along with limited range of motion. Lastly, and perhaps most interestingly, the cricoarytenoid joint is involved in the RA process in 30% of patients. Because this joint is situated near the windpipe, the inflammation can cause difficulty breathing and hoarseness.3
Risks to articular structures in RA are tendon rupture and the formation of synovial cysts. Moreover, median nerve entrapment in the carpal tunnel is commonly seen. A distinguishing feature of RA is that although the disease can affect the neck, it does not involve other areas of the spine, as occurs in other forms of inflammatory arthritis. Another distinguishing examination finding is the presence of subcutaneous rheumatoid nodules, which are found in 20% of patients with RA. These nodules are most often seen over bony prominences; however, they can develop in the lungs, sclerae, and other tissues unrelated to joints. The RA nodules mirror the laboratory findings, as they are related to the presence of RF in serum.5
RA is more than a disease of the joints; it is known to cause problems in many other systems. Sjögren syndrome, characterized by dryness of the eyes, mouth, and mucous membranes, is observed in advanced RA. Scleral nodules can cause other ocular conditions, such as episcleritis, scleritis, and scleromalacia. Cough and progressive dyspnea on examination often indicate the presence of interstitial lung disease in patients with RA. Pericarditis and pleural disease are other comorbidities occasionally seen in RA. It is not uncommon to note mild vasculitis appearing as small hemorrhagic infarcts in the nail folds or finger pulp of patients with RA.4 The current criteria for a diagnosis of RA are presented in Table 1. A score higher than 6 in a possible total of 10 indicates an RA diagnosis.12
Laboratory workup
From 70% to 80% of patients with established RA have serologic titers of anti-cyclic citrullinated peptide (CCP) antibody and RF, which is an IgM antibody that antagonizes the Fc fragment of IgG. RF has a sensitivity of 50% for the detection of RA; anti-CCP antibodies are 95% specific for the disease, and anti-CCP measurement is therefore the most specific blood test for RA. Determining the erythrocyte sedimentation rate (ESR) and C reactive protein (CRP) level in patients with suspected RA is also an integral component of the laboratory workup. The degree of elevation of both these markers tends to mirror the extent of RA pathology in the body.5
