Background: Serum phagocyte-derived alarmins S100A8/9 and S100A12 are considered useful for the assessment of inflammatory diseases. Our study evaluated the use of S100 proteins in a pediatric clinical setting for estimating disease activity and supporting diagnosis.Methods: Patients (n = 136) who had S100 proteins tested as part of clinical care were included in this study and relevant information obtained from the medical record: C-reactive protein (CRP), disease activity status (inactive: = 0 joint; active: > 0 active joint), systemic symptoms in systemic JIA (sJIA), and symptoms of flare of other autoinflammatory and fever syndromes. Patients were categorized as: sJIA, non-systemic JIA (nsJIA), other defined autoinflammatory syndromes (AID) and systemic undifferentiated recurring fever syndromes (SURFS).Results: Patients with sJIA (n = 21) had significantly higher levels of S100A8/9 and S100A12 compared to patients with nsJIA (n = 49), other AIDs (n = 8) or SURFS (n = 14) (all p < 0.0001). Compared to CRP [area under the receiver operating characteristics curve (AUC) = 0.7], S100 proteins were superior in differentiating sJIA from AID and SURFS [AUC = 0.9]. S100A8/9 and S100A12 levels were not associated with disease activity in nsJIA, AID or SURFS. S100A8/9 and S100A12 levels were significantly higher in active sJIA compared to inactive (p = 0.0002 and p = 0.0002 respectively).

BackgroundJuvenile idiopathic arthritis (JIA) is a chronic inflammatory arthritis of unknown origin which can be considered an autoimmune disease (AD). The aim of this study is to analyse the presence of two or more autoimmune diseases (polyautoimmunity) in patients suffering from JIA and to evaluate the occurrence of ADs in their families.MethodsSeventy-nine patients diagnosed with JIA aged 0–21 years, admitted to the Paediatric Rheumatology Unit, Sant’Orsola-Malpighi Hospital, Bologna were screened for ADs. Parents were asked about the presence of ADs in the living relatives of first and second degree.ResultsTwelve of 79 patients (15.2%) had at least 1 AD associated with JIA. Eight patients (10.1%) suffered from autoimmune thyroid disease (AITD), three patients had celiac disease, three patients suffered from psoriasis, one from alopecia and 1 from insulin-dependent diabetes mellitus. The average age at diagnosis was 13.2 years and the cumulative incidence of AITD was 36%. Seventy-six families were studied for a total of 438 relatives. The prevalence of ADs was 13%, greater in first-degree relatives (16.7%) than in second-degree ones (11.1%). The most common AD was AITD; there was no difference in JIA’s age of presentation between patients with positive and negative familiarity with ADs (p > 0.05).ConclusionChildren and adolescents with JIA present a high autoimmunity burden, most commonly represented by AITD. Familial autoimmunity is not negligible in patients suffering from JIA (almost 50% of patients have at least one relative with an AD) and it should always be carefully examined.

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