AB1111 Arthritis is not a prerequisite disease manifestation for the diagnosis of systemic jia: results of a prospective cohort trial using ril-1ra as first line treatment with long term follow-up

Background Systemic onset juvenile idiopathic arthritis (sJIA) is a multifactorial disease, characterised by arthritis, spiking fever, skin rash, lymphadenopathy, hepatosplenomegaly and/or serositis, in combination with increased inflammatory parameters as erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) and ferritin. SJIA is nowadays seen as a complex autoinflammatory disorder. However, in the current ILAR classification, sJIA is still classified under the umbrella of JIA. The past decade has learned that the mechanisms underlying the systemic inflammation in sJIA differ in important aspects from the other subtypes like polyarticular JIA. Objectives Here we compare disease characteristics, manifestations and response to treatment of ILAR-criteria fulfilling sJIA (n=30) and ‘sJIA without arthritis’ (n=12), in order to evaluate whether arthritis should still be a prerequisite for the diagnosis of sJIA. Methods We included 30 consecutive diagnosed and prospectively followed new onset sJIA patients as well as 12 ‘sJIA without arthritis’ from our paediatric rheumatology clinic from 2008 until 2017. The ‘sJIA without arthritis’ patients underwent extensive diagnostic procedures to exlude infections (PCR, blood cultures, serology etc), malignancies (bone marrow punctures, PET scans etc) and other diagnoses. All patients followed a standardised treatment protocol, starting with rIL-1RA (2 mg/kg) as 1st line treatment (without steroids), as previously described(.1 In case of partial response, rIL-1RA dose was raised to 4 mg/kg with a maximum of 200 mg/day. If that failed, corticosteroids were added and/or patients switched to alternative biologicals as canakinumab or tocilizumab. If patients had inactive disease at 3 months after start of rIL-1RA treatment, rIL-1RA was tapered for a month (alternate day regimen) and subsequently stopped. Peripheral blood samples were taken before initiation of rIL-1RA and at all follow-ups for routine lab measurements. For biomarker analyses, serum was isolated at disease onset and at three months after initiation of rIL-1RA. Results There were no differences in disease manifestations like skin rash, serositis, hepatosplenomegaly or symptoms like arthralgic (painful) joint count between sJIA and ‘sJIA without arthritis” patients at diagnosis. Nor was there a difference in the levels of CRP, ESR, ferritin or IL-18 at start of therapy. Importantly, also the response to rIL-1RA treatment did not differ between sJIA and ‘sJIA without arthritis’ patients in our cohort. At last follow-up (median 5,8 years, IQR 2,9–7,6 years), 95% of patients had inactive disease, of which 72% off medication. Conclusions Based upon disease manifestations and inflammatory parameters in patients with confirmed sJIA and ‘sJIA without arthritis’ at disease onset and on excellent treatment responses to a standardised treatment protocol with rIL-1RA as 1st line treatment, we conclude that arthritis should not be a prerequisite disease criterium in the next classification criteria of sJIA. Reference [1] : Vastert, SJet al, Arthritis Rheumatology2014. doi: 10.1002/art.38296. Disclosure of Interest None declared