To define the prevalence of MRI subclinical synovitis in a large cohort of JIA patients in clinical remission and to evaluate its predictive value in terms of disease flare and joint deterioration.
Ninety patients with clinically inactive JIA who underwent a contrast-enhanced (CE) MRI of a previously affected joint were retrospectively included. Each joint was evaluated for synovitis, tenosynovitis and bone marrow oedema (BMO). Baseline and follow-up radiographs were assessed to evaluate structural damage progression.
CE-MRI was acquired in 45 wrists, 30 hips, 13 ankles and 2 knees. Subclinical synovitis was detected in 59/90 (65.5%) patients and BMO in 42/90 (46.7%) patients. Fifty-seven out of 90 (63.3%) patients experienced a disease flare during follow-up. Forty-four out of 59 (74.6%) patients with subclinical synovitis experienced a disease flare versus 13/31 (41.9%) patients with no residual synovitis on MRI (p=0.002). The presence of subclinical synovitis was the best predictor of disease flare on multivariable regression analysis (HR= 2.45; p=0.003). Baseline and follow-up radiographs were available for 54 patients; 17/54 (31.5%) patients experienced radiographic damage progression. BMO (HR=4.40; p=0.045) and age > 17 years (HR= 3.51; p=0.04) were strong predictors of joint damage progression in the multivariable analysis.
MRI-detected subclinical inflammation was present in a large proportion of patients with JIA despite clinical remission. Subclinical synovitis and BMO have been shown to play a role in predicting the risk of disease relapse and joint deterioration, with potential implications for patients' management.