ObjectivesJuvenile myositis is a rare and heterogeneous disease. Diagnosis is often difficult but early treatment is important in reducing the risk of associated morbidity and poor outcomes. Myositis specific autoantibodies have been described in both juvenile and adult patients with myositis and can be helpful in dividing patients into clinically homogenous groups. We aimed to explore the utility of myositis specific autoantibodies as diagnostic and prognostic biomarkers in patients with juvenile-onset disease.MethodsUsing radio-labelled immunoprecipitation and previously validated ELISAs we examined the presence of myositis specific autoantibodies in 380 patients with juvenile-onset myositis in addition to, 318 patients with juvenile idiopathic arthritis, 21 patients with juvenile-onset SLE, 27 patients with muscular dystrophies, and 48 healthy children.ResultsAn autoantibody was identified in 60% of juvenile-onset myositis patients. Myositis specific autoantibodies (49% patients) were exclusively found in patients with myositis and with the exception of one case were mutually exclusive and not found in conjunction with another autoantibody. Autoantibody subtypes were associated with age at disease onset, key clinical disease features and treatment received.ConclusionsIn juvenile patients the identification of a myositis specific autoantibody is highly suggestive of myositis. Autoantibodies can be identified in the majority of affected children and provide useful prognostic information. There is evidence of a differential treatment approach and patients with anti-TIF1γ autoantibodies are significantly more likely to receive aggressive treatment with IV cyclophosphamide and/or biologic drugs, clear trends are also visible in other autoantibody subgroups.

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Juvenile idiopathic arthritis (JIA) is the most common paediatric rheumatological disorder and is classified by subtype according to International League of Associations for Rheumatology criteria. Depending on the number of joints affected, presence of extra-articular manifestations, systemic symptoms, serology and genetic factors, JIA is divided into oligoarticular, polyarticular, systemic, psoriatic, enthesitis-related and undifferentiated arthritis. This review provides an overview of advances in understanding of JIA pathogenesis focusing on aetiology, histopathology, immunological changes associated with disease activity, and best treatment options. Greater understanding of JIA as a collective of complex inflammatory diseases is discussed within the context of therapeutic interventions, including traditional non-biologic and up-to-date biologic disease-modifying anti-rheumatic drugs. Whilst the advent of advanced therapeutics has improved clinical outcomes, a considerable number of patients remain unresponsive to treatment, emphasising the need for further understanding of disease progression and remission to support stratification of patients to treatment pathways.

A higher proportion of patients with juvenile-onset systemic lupus erythematosus (JSLE) will have renal involvement compared with adult-onset disease, some progressing to renal failure in adulthood. Histological examination is the gold standard for diagnosing lupus nephritis (LN), but its invasive nature limits routine use. Using cross-sectional cohort analysis, we aimed to determine whether urinary concentrations of monocyte chemoattractant protein-1 (MCP1), alpha-1-acid glycoprotein (AGP) and interferon-inducible protein 10 (IP10) are biomarkers of active LN. Sixty JSLE patients recruited to the UK JSLE Cohort Study were categorized according to the British Isles Lupus Assessment Group (BILAG) activity index. Patients with active renal JSLE (n = 8; renal BILAG score A, B) had significantly higher urinary MCP1 concentrations than patients with inactive renal disease (n = 52; renal BILAG score C, D, E; 582 pg/mg creatinine [Cr], 207 pg/mg Cr; p = 0.018) or healthy controls (n = 23; 117 pg/mg Cr; p = 0.005). Urinary AGP concentration was significantly elevated in patients with active renal disease compared with inactive renal disease (1517 ng/mg Cr, 485 ng/mg Cr; p = 0.027) or healthy controls (313 ng/mg Cr; p = 0.013). Urinary IP10 concentration was not significantly different between groups, but did strongly correlate with uMCP and uAGP levels (rho = 0.38, p = 0.009; rho = 0.33, p = 0.021). Urinary MCP1 and AGP are biomarkers of LN, providing insight into its pathophysiology. Longitudinal studies are warranted.