One of the newest classifications for this disorder involving extensive pustule formation. Diagnose is based on medical history, physical examination, blood studies and x-rays of joints with symptoms. The agglutination test of blood shows a negative rheumatoid factor. Synovial fluid is also analyzed for the presence of uric acid to rule out gout. Additionally, psoriatic arthritis is more asymmetrical than traditional rheumatoid arthritis.
Psoriasis is similar to rheumatoid arthritis in numerous ways.
For instance, both have subcutaneous rheumatoid nodules in twenty percent of patients. The histology of both disorders is also very similar. Reiter's disease and Keratoderma blennorrhagicum are frequently present in patients possessing either of these disorders. However, there are also some notable differences between these disorders such as the fact that psoriatic arthritis has an earlier onset, involves a smaller number of joints and tends to be less disabling than rheumatoid arthritis. Additionally, rheumatoid arthritis affects proximal joints while psoriatic arthritis affects distal joints.