eMedicine Specialties > Physical Medicine and Rehabilitation > Arthritis & Connective Tissue Disorders

Rheumatoid Arthritis: Differential Diagnoses & Workup

Author: Kavita Gupta, DO, MEng, Department of Orthopedics, Center of Physical Medicine and Rehabilitation, University of Dentistry and Medicine of New Jersey
Coauthor(s): Sarjoo M Bhagia, MD, Honorary Teaching Faculty, Charlotte Institute of Rehabilitation, Consulting Staff, Physical Medicine and Rehabilitation, OrthoCarolina
Contributor Information and Disclosures

Updated: Apr 5, 2009

Differential Diagnoses

Osteoarthritis
Systemic Lupus Erythematosus

Other Problems to Be Considered

The differentiation of rheumatoid arthritis (RA) from other diseases of connective tissue can be difficult; however, certain clinical features are helpful. Rheumatic fever is characterized by the migratory nature of the arthritis, an elevated antistreptolysin titer, and a more dramatic and prompt response to aspirin. Carditis and erythema marginatus may occur in adults, but chorea and subcutaneous nodules virtually never do. Butterfly rash, discoid lupus erythematosus, photosensitivity, alopecia, a high titer to anti-DNA, renal disease, and central nervous system abnormalities suggest the diagnosis of systemic lupus erythematosus (SLE).

Degenerative joint disease is not associated with constitutional manifestations; in contrast to the morning stiffness of RA, the joint pain from degenerative joint disease is characteristically relieved by rest. Signs of articular inflammation prominent in RA are usually minimal in degenerative joint disease. In contrast to RA, osteoarthritis spares the wrist and the MCP joints. While in the early years, gouty arthritis is almost always intermittent and monarticular, in later years it can become a chronic polyarticular process that mimics RA. Gouty tophi can at times resemble rheumatoid nodules. The early history of intermittent monarthritis and the presence of synovial urate crystals are distinctive features of gout.

Pyogenic arthritis can be distinguished by chills and fever, demonstration of the causative organism in joint fluid, and the frequent presence of a primary focus elsewhere (eg, gonococcal arthritis). Chronic Lyme disease typically involves only 1 joint, most commonly the knee, and is associated with positive serologic tests. Human parvovirus B19 infection in adults can occasionally mimic RA. Polymyalgia rheumatica occasionally causes polyarthritis in patients older than 50 years, but these patients have chiefly proximal muscle pain and stiffness and remain negative for rheumatoid factor (RF).

A variety of cancers produce paraneoplastic syndromes, including polyarthritis. One form is hypertrophic pulmonary osteoarthropathy, which is most often produced by lung and gastrointestinal carcinomas. Hypertrophic pulmonary osteoarthropathy is characterized by a rheumatoidlike arthritis associated with clubbing, periosteal new bone formation, and a negative rheumatoid factor. Diffuse swelling of the hands with palmar fascitis also has been reported with a variety of cancers, especially ovarian carcinoma.

Workup

Laboratory Studies

• Serum protein abnormalities are often present. Rheumatoid factor (RF), an immunoglobulin M (IgM) antibody directed against the Fc fragment of immunoglobulin G (IgG), is present in the sera of more than 75% of patients. High titers of RF are commonly associated with severe rheumatoid disease. Antinuclear antibodies are demonstrable in 20% of patients, though their titers are lower in rheumatoid arthritis than in SLE. During the acute and chronic phases, the erythrocyte sedimentation rate and gamma globulins (commonly IgM and IgG) are usually elevated; however, leukopenia may occur in the presence of splenomegaly (Felty syndrome). The platelet count often is elevated, roughly in proportion to the severity of overall joint inflammation. Joint fluid examination is valuable, reflecting abnormalities that are correlated with varying degrees of inflammation.

Imaging Studies

• Plain radiographs
  • Radiography is the most specific workup study for rheumatoid arthritis.
  • Radiographs taken during the first 6 months typically are read as negative because of decreased sensitivity during that period.
  • The earliest changes occur in the wrists or feet and consist of soft-tissue swelling and juxta-articular demineralization. (See image below and Image 6.) Later, diagnostic changes of uniform joint-space narrowing are evident, and erosions develop. The erosions are often first evident at the ulnar styloid and at the juxta-articular margins, where the bony surface is not protected by cartilage.

• Diagnostic changes also occur in the cervical spine with C1-2 subluxation, but these changes usually take several years to develop.
• Nuclear imaging studies
  • Nuclear imaging studies are quite sensitive for detecting many disease processes, and the entire body can be imaged at once. However, this technique is not specific because of the number of disease processes that may cause radionuclide accumulation.
  • When areas of increased uptake are observed, additional studies such as radiography are usually necessary to specify the type of abnormality.
  • Joints affected by inflammatory or degenerative arthritis demonstrate increased uptake and can map the extent of disease in a single examination.
  • In a patient with inflammatory arthritis and widespread changes on radiographs, scintigraphy may help to locate areas of early active inflammation.

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