What Is Psoriatic Arthritis?

By jolene

Reviewed: Dr. Mera

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Psoriatic arthritis is a chronic and inflammatory condition that develops in about 5% of patients with psoriasis. Although a link between psoriasis and arthritis was made in the mid-19th century, it was not clinically distinguished from rheumatoid arthritis until the 1960s.

As the name suggests, psoriatic arthritis affects the joints and entheses (connective tissue between bone and ligament or tendon). Psoriatic arthritis may also affect the nails and skin with other associated features such as osteitis, uveitis, and dactylitis. Ninety-five percent of patients with psoriatic arthritis experience peripheral joint disease while axial spine involvement occurs in the other 5%.

1. Mechanism

Although the pathogenesis of psoriatic arthritis is not fully understood, environmental factors, genetics, and immune-mediated inflammation are believed to play a role. Since psoriatic arthritis and psoriasis are interrelated disorders, both disorders have commonalities in the pathogenesis. Genetic factors play an important role in the susceptibility of psoriatic arthritis and psoriasis with an estimated 40% of patients having a positive family history. The recurrence risk ratio has been estimated to be 8 to 10 for psoriasis and 30 to 55 in psoriatic arthritis. The inflammatory process also suggests the involvement of immunological mechanisms where there is an increased level of proinflammatory cytokines such as IL8 and IL6.