Symmetrical polyarthritis may resemble rheumatoid arthritis, though the rheumatoid factor test should be negative. Uncertainty about classification is reasonable because psoriasis and rheumatoid arthritis are both relatively common diseases and are expected to occur together by chance. Dominant or exclusively distal interphalangeal joint involvement with psoriatic nail changes may occur. An elevated erythrocyte sedimentation rate, anemia, and hyperuricemia may be found. Rheumatoid factor and antinuclear antibody tests are negative.
Synovial fluid shows nonspecific inflammatory changes.
Gold, penicillamine, and hydroxychloroquine are not useful agents. Psoriatic arthritis usually runs a more benign course than rheumatoid arthritis. Most patients with psoriatic arthritis maintain reasonable function, often despite impressive deformities.