Laboratory features of psoriatic arthritis.

Psoriatic arthritis (PA) is regarded as a disease which belongs to the seronegative polyarthritis with a broad clinical pattern. Because of the involvement of the skin and the inflammatory processes in the joints, the disease is of interest to both the rheumatologist and the dermatologist. There are no laboratory findings which are specific to PA, although some abnormalities have been published in the literature with different bases for comparison: PA and healthy people, PA and rheumatoid arthritis (RA), or PA and skin psoriasis. The most probable reason for some of the divergent data found in the literature might be the heterogeneity of the disease, whereby the results represent a mixture of the subtypes of PA. The present paper summarizes the main findings in PA that have been reported in the literature, including the "traditional laboratory findings" and some immunological and biochemical data.