Persistent low grade synovitis without erosive progression in magnetic resonance imaging of rheumatoid arthritis patients treated with infliximab over 1 year

Disease remission is only reached by a minority of rheumatoid arthritis (RA) patients treated with infliximab. Radiological assessment reported in clinical trials support the view that even under persistent inflammatory activity there is no further structural damage. Magnetic resonance imaging (MRI) allows a highly accurate detection of synovitis, bone edema, and erosions, constituting the ideal instrument for the evaluation of treatment response. The goal of this study was to evaluate MRI changes over 1 year in RA patients treated with infliximab. Four RA patients refractory to methotrexate (MTX) therapy were treated with infliximab 3 mg/kg 8/8 weeks and followed up for 1 year. Disease Activity Score (DAS28) was measured in the day of each infliximab administration. MRI was performed at baseline, 3 months, and 1 year. A simplified OMERACT RA MRI scoring (RAMRIS) was applied to the dominant wrist: synovitis (0-3) was measured in the intercarpal-carpometacarpal joints (CMTJ); bone edema (0-39) and erosions (0-130) in the base of the metacarpal and wrist bones. Baseline DAS28 was superior to 3.2 in all patients (ranging from 4.8 up to 6.2). At 14 weeks, DAS28 was still superior to 3.2 (ranging from 3.5 up to 4.6) and at 46 weeks all patients have responded, however without having achieved clinical remission, as DAS28 was still above 2.6 (ranging from 2.6 up to 3.4). MRI showed that synovitis was reduced in all patients to a score of 1, bone edema was slightly reduced (10% reduction), and erosive score was unchanged (baseline values ranging from 2 up to 20). Despite persistent low disease activity, these four RA patients treated with infliximab had stable simplified RAMRIS erosive scores over 1 year. These results support the view that there might be an uncoupling process between inflammation and bone erosions when tumor necrosis factor alpha is targeted in RA.