Psoriasis and arthritis. III. A cross-sectional comparative study of patients with "psoriatic arthritis" and seronegative and seropositive polyarthritis: radiological and HLA aspects.

In a group of patients with seronegative polyarthritis and psoriasis, the radiological features and the incidence of histocompatibility antigens were compared with those of a group of patients with seronegative polyarthritis but not psoriasis. No radiological criteria proved to be characteristic of psoriatic arthritis. In the group of patients with seronegative polyarthritis and psoriasis, erosions of the distal interphalangeal (DIP) joints were seen more frequently and were more severe than in the group of patients with seronegative arthritis without psoriasis. For the group of patients with seronegative polyarthritis and psoriasis, correlation was found between psoriatic nail lesions and erosions of the DIP joints, but this correlation was not found between the nail involvement and erosion of the adjacent DIP joint. No significant differences were found for the incidence of histocompatibility antigens between patients with seronegative polyarthritis with or without psoriasis. However, differences were found between these two groups and either the seropositive polyarthritis group or blood bank donors.