A8: Juvenile Idiopathic Arthritis with Dry Synovitis: Clinical and Imaging Aspects in a Cohort of 10 Patients

Abstract

Background/Purpose:Dry synovitis is considered to be a rare form of JIA, incompletely understood and following a potentially destructive course. Since its first description only a few reports mention this entity within the spectrum of JIA. We aimed to describe the clinical and radiological manifestations, and the course of dry synovitis and to compare it with classical RF negative polyarticular JIA.Methods:A retrospective study of 10 patients in 3 pediatric rheumatology centers who presented with 1. progressive, symmetric polyarticular stiffness with limitations and without clinical synovitis, 2. radiologic signs of articular damage and 3. Absence of inflammatory parameters (CRP, ESR). Neuromuscular conditions and metabolic storage/bone disorders were excluded. This cohort was compared with 35 consecutive patients with classical polyarticular RF negative JIA. Clinical, laboratory and imaging (X‐rays, MRI) data of both groups were reviewed.Results:The dry synovitis cohort included 4 boys and 6 girls. The median (range) age at first manifestation and diagnosis were respectively 4.3 yrs (1.1–8.9) and 7.3 yrs (2.8–14). Presenting signs comprised delayed motor development and/or progressive articular stiffness. Pain complaints emerged with time. Clinical examination showed a symmetric polyarticular involvement without clinical signs of synovitis. CRP was normal and ESR < 8mm/h. In 9/10 patients ANA were absent. Radiological imaging (wrist, ankles and/or pelvis) showed osteopenia, advanced bone age, cartilage loss and/or bone erosions in all patients. MRI revealed synovial thickening in 9/10 patients; bone edema was variably present and bone erosions were demonstrated in 8/10 patients. Treatments comprised NSAIDs (n = 8/10), corticosteroids (n = 8/10), methotrexate (n = 9/10), anti‐TNF (n = 6/10), IL‐1 receptor antagonist (n = 1/10) and resulted in some subjective improvement. However articular limitations persisted and imaging showed progressive (osteo)articular damage. The comparison of the dry synovitis with polyarticular JIA patients showed that the age at disease onset was comparable in the 2 groups. Significant differential features found in the dry synovitis cohort were higher diagnostic delay, increased number of joint involvement and contractures, lack of swelling and tenderness, and lack of increased acute phase response (CRP, ESR) and ANA.Conclusion:From our data, we conclude that ‘dry synovitis’ can be considered as a clinical descriptive term referring to the development of progressive symmetric polyarticular limitations. We show that MRI is usefull in demonstrating underlying subclinical inflammation and in combination with clinical features and standard X‐rays helpful in the differential diagnosis with mucopolyssaccharidosis, neuromuscular disorders and bone dysplasia. Clinical as well as radiological evolution seem to be refractory to the current JIA therapy and to be different among patients diagnosed with ‘dry synovitis,’ suggesting that this clinical manifestation may represent a heterogeneous spectrum of joint and/or bone disorders. The exact nature of this entity and a possible contribution of a metabolic or intrinsic bone disorder into its pathogenesis remain to be determined.