Magnetic resonance imaging identifies features in clinically unaffected knees predicting extension of arthritis in children with monoarthritis.

OBJECTIVE

A proportion of children with oligoarthritis have an aggressive disease course. Identifying these children at presentation would help guide prognosis and management. We examined if magnetic resonance imaging (MRI) of clinically unaffected joints is more sensitive than clinical assessment in identifying those at risk of developing arthritis in more than one joint.

METHODS

Ten children were recruited; they had a mean age of 9.4 (range 5.2-14.2) years at presentation of a monoarthritis. MRI of a clinically unaffected knee was performed within 4 months of presentation, and was reported by 2 pediatric radiologists blinded to the clinical findings. All MR examinations included post-gadolinium sequences. Joints with clinically apparent arthritis were recorded regularly over a median of 37.0 (range 6.6-47.0) months by a median of 6.0 (range 2-8) pediatric rheumatologists blinded to the MR result.

RESULTS

Four children developed arthritis in other joints over a median of 3.9 (range 3-6) months after the MRI scan; all had abnormal MRI scans at presentation. Three of these developed clinical features in the previously normal knee 4-11 months after MRI identified small joint effusions, synovial hypertrophy, and lymph node enhancement. One child developed a polyarthritis, but never developed clinical features in the imaged knee over 3.8 years of followup. Four other children had a persistent monoarthropathy with a median followup of 29.5 (range 6.6-42.0) months. All 4 had normal MRI. Two children had reactive arthritis.

CONCLUSION

MRI distinguished between patients with a persistent monoarthritis and those who developed further clinical arthritis up to 1 year later. The results suggest a widespread inflammatory process may exist in children whose arthritis extends, and this has implications for our understanding of disease and the design and timing of therapeutic interventions.