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What Else Looks Like Psoriatic Arthritis

Rheumatoid Arthritis

Psoriatic arthritis and rheumatoid arthritis are both inflammatory forms of arthritis, presenting with pain and swelling in the affected joints and reduced function. These forms of arthritis are usually associated with morning stiffness, which usually improves with activity and is aggravated by rest. Rheumatoid arthritis affects women more than men, its peak incidence is in the 4th decade. Is usually affects the small and medium size joints in a symmetric polyarthritis. Psoriatic arthritis differs from rheumatoid arthritis in the following features:

  • Equal gender frequency
  • Involvement of the end joints of the fingers and toes with usually does not occur in rheumatoid arthritis
  • Asymmetric distribution, with different joints being involved in both sides of the body
  • “Ray distribution” where all joints of one digit are affected rather then joints at the same level in a symmetric distribution
  • Discoloration over the affected joint which is unusual in rheumatoid arthritis
  • Presence of Dactylitis – swelling of the whole digit (sausage digit)
  • Presence of Enthesitis – inflammation at the insertion of tendons into bone.
  • Presence of Spondylitis – inflammation in the joints of the back which is distinctly unusual in rheumatoid arthritis
  • Lack rheumatoid factor in the majority of the patients
  • Presence of nail lesions
  • Different genetic predisposition
  • Different extra-articular features


Another form of arthritis that may be confused with psoriatic arthritis is osteoarthritis. Osteoarthritis is considered a non-inflammatory form of arthritis. It affects women more commonly and affects large joints such as hips and knees, as well as the end joints of the fingers. It can also affect the joints of the spine with resulting degenerative arthritis. When distal joint involvement occurs in an older person with psoriasis the diagnosis may be difficult. Psoriatic arthritis may be differentiated from osteoarthritis by:

  • The inflammatory nature of the distal joint disease in psoriatic arthritis
  • The inflammatory nature of back involvement in psoriatic arthritis
  • The presence of psoriatic nail lesions

Reiter’s Arthritis

Reactive arthritis is a condition that may be confused with psoriatic arthritis. Like psoriatic arthritis it involves both peripheral joints and spine, and there is skin involvement which sometimes may be very difficult to differentiate from psoriasis. However, Reactive arthritis tends to affect men more commonly at an earlier age that psoriatic arthritis. It is associated with pink eye, and inflammation in the urethra. It usually affects the large joints of the legs.

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