Background Dry synovitis (DS) is considered to be a rare form of juvenile idiopathic arthritis (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.
Objectives To describe the clinical and radiological manifestations and clinical course of DS and to compare it with classic polyarticular RF negative JIA (c-poly JIA).
Methods We performed a retrospective study of 10 patients followed in 3 pediatric rheumatology centers who presented with progressive articular limitations without clinical synovitis and radiologic signs of articular damage. This cohort was compared with a cohort of 35 consecutive patients with classical polyarticular RF negative JIA, seen at the Pediatric Rheumatology Unit of Padua in the period January-June 2012. Clinical, laboratory and imaging (X-rays, MRI) data of both groups were reviewed and compared. Treatment was grouped in 4 categories: no treatment, just corticosteroids (CS), Methotrexate (MTX) + CS, Biological agents (BA) + MTX. Outcome measures included growth, remission state as: clinical remission without medication (CR), clinical remission on medication (CRM), progressive arthropathy with mild functional disability (PA), severe arthropathy with ankylosis and irreversible disability (SA).
Results The cohort included 4 male and 6 female, mean (range) age at first manifestation and diagnosis were respectively 4.3 yrs (1.3-8.5) and 7.3 yr (2.8-14). Presenting signs included delayed motor development, progressive articular stiffness and contractures. Little or no pain was present. Clinical examination showed a symmetric and polyarticular involvement without clinical signs of synovitis. CRP was normal in all and ESR>20mm/h in 1/10. In 9/10 patients ANA were absent. Radiological imaging showed osteopenia and/or 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), biological agents (anti-TNF, IL-RA) (n=6/10). The comparison of DS with c-poly JIA showed that the age at disease onset and at diagnosis were comparable in the two groups. Significant differential features of DS resulted: higher diagnostic delay, increased number of joint involved and joint contractures, lack of swelling/tenderness, prevalent upper limbs involvement, lack of acute phase reactants (ESR, CRP) and no ANA detection. X-ray revealed a significant higher prevalence of osteopenia, erosions and bone edema at MRI in DS. At the last evaluation 77% of patients with c-poly JIA were in CR or CRM while 50% of DS had PA. Growth was significantly impaired in DS (p 0.016).
Conclusions Dry Synovitis is actually considered as a subtype of polyarticular JIA. Our study clearly shows that it represents a distinct and unique entity characterized by increased number of joint involved and contractures, prevalent upper limbs involvement, progressive course and lack of acute phase reactants or autoantibodies elevation. The exact nature of DS entity and the possible contribution of metabolic or intrinsic bone disorders into its pathogenesis remain to be determined.
Disclosure of Interest None Declared