Immunomodulating Drugs in the Management of Psoriatic Arthritis

Psoriatic arthritis is a chronic inflammatory arthropathy which can be distinguished from rheumatoid arthritis on the basis of differing patient demographics, genetic predisposition, histopathologic change, radiographic appearance, and clinical course. The cause of psoriatic arthritis remains unknown but appears to be autoimmune in nature as its pathogenesis is characterized by persistent synovial inflammation resulting in damage to the articular cartilage and osteolysis. Compared with rheumatoid arthritis, distinct lymphocyte subpopulations and pro-inflammatory cytokine levels appear to be present within the joint but the importance and therapeutic implications of these differences is uncertain. The clinical presentation of psoriatic arthritis is variable and overlapping patterns of joint involvement affecting both the appendicular and axial skeleton are seen. For patients with mild synovial disease and a favorable prognosis, the use of a nonsteroidal anti-inflammatory drug for symptomatic relief is often sufficient. However, the destructive potential of psoriatic arthritis is increasingly recognized and patients with more synovial disease and radiographic change at presentation appear to be at risk for greater morbidity and increased mortality.

Immunomodulating therapy has the potential to suppress joint inflammation and preserve functional capacity but true disease modification has yet to be shown. The toxicity associated with presently available immunomodulatory agents makes careful patient selection and conscientious monitoring essential. The efficacy of methotrexate and sulfasalazine in patients with psoriatic arthritis is well defined while more anecdotal reports of benefit exist for other agents including the antimalarials, azathioprine, colchicine, cyclosporine, and the retinoids. For all treatment regimens, the magnitude of clinical improvement demonstrated to date has been rather small and quite subjective in character with few controlled studies of adequate size and duration having been reported. Emerging biologic therapies, such as those which target tumor necrosis factor, will hopefully provide future treatment options with greater efficacy and improved safety for patients with psoriatic arthritis.