How is psoriatic arthritis related to psoriasis?

Psoriatic arthritis is a form of inflammatory arthritis that occurs in approximately 10 to 30 percent of individuals who have psoriasis, an immune-mediated skin condition characterized by raised, red, scaly plaques.1

The relationship between the two conditions is defined by the following clinical patterns:

• Temporal Sequence: Psoriatic arthritis typically develops years after the onset of psoriasis. However, in some instances, the arthritis may precede the skin symptoms, or both conditions may appear simultaneously.1
• Pathological Classification: Psoriatic arthritis is categorized as a spondyloarthropathy, a group of related inflammatory conditions that also includes ankylosing spondylitis and arthritis associated with inflammatory bowel disease.1
• Clinical Presentation: Unlike rheumatoid arthritis, psoriatic arthritis is not associated with elevated levels of serum rheumatoid factor. It often presents with enthesitis (inflammation where tendons or ligaments attach to bone) and dactylitis, a characteristic swelling of the fingers and toes. While it can eventually affect the axial joints, it frequently impacts the outer joints of the fingers and toes and can lead to significant bone destruction.12