Subclinical joint involvement in psoriasis: magnetic resonance imaging and X-ray findings.

Previous studies have shown that magnetic resonance imaging is more sensitive in assessing soft tissue and bone involvement in inflammatory arthritis than conventional radiography. Therefore the main objects of this study were to evaluate the frequency of hand involvement in psoriatic patients free from arthritic symptoms, and to compare the results with those of a healthy control population (age- and sex-matched). Twenty-five patients suffering from active nummular and/or plaque psoriasis with no arthritic signs or symptoms were studied together with 12 healthy control subjects. The articular structures of both hands in all patients were screened using both traditional radiological techniques and magnetic resonance imaging. Specifically, we examined: soft tissue swelling, periarticular effusion, joint effusion-synovial pannus, tendon sheath effusion, bone erosion, luxation, sub-luxation, bone cysts and subchondral signal intensity abnormalities. Sixty-eight percent of our psoriatic patients were found to be positive with at least one arthritic sign using magnetic resonance imaging, while with the standard X-ray procedure, only 32% of the same group of patients were found to be positive. Specifically, abnormal signal intensity in the subchondral focal areas were seen in 9 patients using the magnetic resonance imaging technique, while in the control group, no significant abnormalities were detected. A high percentage of psoriatic patients without apparent arthritic signs and symptoms were shown to have hand articular involvement, in particular in the distension of the capsular and periarticular oedema when examined with magnetic resonance imaging. In our experience, the use of magnetic resonance imaging allows a clear and adequate evaluation of the cartilage, bone and soft tissue material, and is diagnostically superior to X-ray in demonstrating clinically silent and radiologically invisible articular lesions. Moreover, the subchondral changes detected by magnetic resonance imaging were unexpected findings which could imply an ischaemic origin.