Magnetic resonance imaging of the hand in psoriatic arthritis.

Although magnetic resonance imaging (MRI) studies of psoriatic arthritis (PsA) are fewer than those of rheumatoid arthritis (RA), interest in this field is growing. The type and site of the lesions, rather than the mere severity of synovitis, can help differentiate PsA from other arthritides. Extracapsular enhancement and enthesitis are features emphasized as typical of PsA, but their relevance for the diagnosis is more quantitative than qualitative. Erosions in PsA are probably less frequent and progressive than in RA. Bone edema is unlikely to predict the appearance of erosions in patients with PsA. The Rheumatoid Arthritis Magnetic Resonance Imaging Scoring (RAMRIS) system has been adapted to peripheral PsA, but standardization is still in progress. Dactylitis is a relatively specific feature of PsA. Its pathogenic mechanisms have been investigated with MRI. MRI evaluation of PsA may facilitate diagnosis, evaluation of treatment effects, and understanding of associated mechanisms.