Dynamic contrast-enhanced MRI revealed different patterns of inflammation between rheumatoid and psoriatic arthritis in the hands and wrists of afflicted patients, researchers found.
The relative, or late enhancement, 15 minutes after injection of contrast material in rheumatoid arthritis, ranged from 140.6% to 333.9%, while that for psoriatic arthritis was 92.5% to 303.9% (P=0.007), according to Nina F. Schwenzer, MD, and colleagues from the University Hospital of Tübingen in Germany.
In comparison, no difference in the relative enhancement was seen after 35 seconds, 52 seconds, or three minutes after injection of the contrast material (P=0.695, P=0.573, and P=0.278, respectively), the researchers reported in the March American Journal of Roentgenology.
There also were no differences in the rate of early enhancement per second at 35 and 52 seconds (P=0.704, P=0.564, respectively).
Unlike past practice, treatment for psoriatic arthritis today cannot simply be patterned after that used for rheumatoid arthritis, because some of the new biologic agents are ineffective or not approved for psoriatic arthritis.
It can be difficult to differentiate the two conditions clinically, however -- particularly with the polyarticular rheumatoid-like pattern of psoriatic arthritis.
And, although laboratory findings can be helpful in supporting a diagnosis of rheumatoid arthritis if rheumatoid factor and cyclic citrullinated peptide antibodies are positive, some 30% of rheumatoid arthritis patients are seronegative for these antibodies.
There are similarities in the inflammatory processes associated with the two conditions, with invasion of the synovium by activated B or T cells and macrophages, as well as by molecular mediators such as tumor necrosis factor alpha and interleukins.
However, differences have also been identified histopathologically, with the synovium in psoriatic arthritis characterized by a greater number of vessels and a thickening of capillary and small arterial walls.
http://www.medpagetoday.com/Rheumatology/Arthritis/18627ttt