Psoriatic arthritis

Psoriatic arthritis is an inflammatory arthritis that can be distinguished from rheumatoid arthritis by unique clinical manifestations, characteristic radiographic findings and the absence of rheumatoid factor [1]. Patients often present with focal inflammation at multiple sites involving the skin, joints, and tendon insertion sites or entheses. Potentially revealing clues to the pathogenesis of PsA are provided by several observations, which include the strong family history of psoriasis in many psoriatic arthritis patients, the association of skin and joint disease with class I major histocompatability alleles, the equal frequency in men and women, and reports that skin and joint inflammation can be triggered or worsened by a variety of environmental factors. Taken together, these elements are compatible with a polygenetic disorder that is modulated by external stimuli. Unfortunately, until recently, the disease mechanisms underlying joint inflammation in the psoriatic joint were largely unknown. Recent advances in immunology, molecular biology and imaging techniques, however, have provided a new understanding of key events fostering inflammation in psoriatic skin and joints.Moreover, the arrival of targeted biological therapies has greatly improved treatment responses and provided novel opportunities for understanding the contribution of specific effector cell populations to ongoing inflammation and defining the role of both proand anti-inflammatory cytokines in vivo [2].