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Objective. To investigate the safety and efficacy of a recombinant human anti-interleukin-6 (anti-IL-6) receptor monoclonal antibody (MRA) that indirectly inhibits the effects of IL-6 in children with systemiconset juvenile idiopathic arthritis (JIA) refractory to high-dose, long-term corticosteroids.Methods. An individual escalating-dose trial was conducted in 11 children with active systemic-onset JIA who met the inclusion criteria. All were first administered an intravenous dose of 2 mg/kg MRA. Each child without active inflammation was given a second identical dose 2 weeks later and a third identical dose 2 weeks after the second dose. Children with disease flares according to laboratory marker values received a 4-mg/kg dose. Those without disease flares at this dose received a second 4-mg/kg dose 2 weeks later and a third 4-mg/kg dose 2 weeks after the second dose, while those with active inflammation received an additional 3 doses of 8 mg/kg MRA. Efficacy was evaluated every 2 weeks according to responses on the JIA core set of improvement criteria and the results of laboratory tests.Results. MRA abruptly reduced disease activity in 10 of the 11 children, as assessed by the occurrence of febrile episodes, active arthritis, scores on the Childhood Health Assessment Questionnaire, and levels of acute-phase reactants. However, levels of inflammatory reactants fluctuated until the proper MRA dose for each child was reached. Two weeks after the third fixed dose of MRA, 90.9% of all patients had a 30% improvement response, 90.9% had a 50% improvement response, and 63.6% had a 70% improvement response.Conclusion. MRA treatment of children with active systemic disease results in clinical improvement and in normalized levels of acute-phase reactants. MRA was safe and well tolerated and provided greater clinical benefit than conventional corticosteroids, considering the ill effects of IL-6 and adverse events.

Objective Chronic infantile neurologic, cutaneous, articular (CINCA) syndrome, also known as neonatal-onset multisystem inflammatory disease (NOMID), is a dominantly inherited systemic autoinflammatory disease. Although heterozygous germline gain-of-function NLRP3 mutations are a known cause of this disease, conventional genetic analyses fail to detect disease-causing mutations in ~40% of patients. Since somatic NLRP3 mosaicism has been detected in several mutation-negative NOMID/CINCA syndrome patients, we undertook this study to determine the precise contribution of somatic NLRP3 mosaicism to the etiology of NOMID/CINCA syndrome. Methods An international case–control study was performed to detect somatic NLRP3 mosaicism in NOMID/CINCA syndrome patients who had shown no mutation during conventional sequencing. Subcloning and sequencing of NLRP3 was performed in these mutation-negative NOMID/CINCA syndrome patients and their healthy relatives. Clinical features were analyzed to identify potential genotype–phenotype associations. Results Somatic NLRP3 mosaicism was identified in 18 of the 26 patients (69.2%). Estimates of the level of mosaicism ranged from 4.2% to 35.8% (mean ± SD 12.1 ± 7.9%). Mosaicism was not detected in any of the 19 healthy relatives (18 of 26 patients versus 0 of 19 relatives; P < 0.0001). In vitro functional assays indicated that the detected somatic NLRP3 mutations had disease-causing functional effects. No differences in NLRP3 mosaicism were detected between different cell lineages. Among nondescript clinical features, a lower incidence of mental retardation was noted in patients with somatic mosaicism. Genotype-matched comparison confirmed that patients with somatic NLRP3 mosaicism presented with milder neurologic symptoms. Conclusion Somatic NLRP3 mutations were identified in 69.2% of patients with mutation-negative NOMID/CINCA syndrome. This indicates that somatic NLRP3 mosaicism is a major cause of NOMID/CINCA syndrome.

Cryopyrin-associated periodic syndrome (CAPS) is a spectrum of systemic autoinflammatory disorders in which the majority of patients have mutations in the coldinduced autoinflammatory syndrome (CIAS)1 gene. Despite having indistinguishable clinical features, some patients lack CIAS1 mutations by conventional nucleotide sequencing. We recently reported a CAPS patient with mosaicism of mutant CIAS1, and raised the possibility that CIAS1 mutations were overlooked in "mutation-negative" patients, due to a low frequency of mosaicism. To determine whether there were latent mutant cells in "mutation-negative" patients, we sought to identify mutation-associated biologic phenotypes of patients' monocytes. We found that lipopolysaccharide selectively induced necrosis-like cell death in monocytes bearing CIAS1 mutations. Monocyte death correlated with CIAS1 up-regulation, was dependent on cathepsin B, and was independent of caspase-1. Cell death was intrinsic to CIAS1-mutated monocytes, was not mediated by the inflammatory milieu, and was independent of disease severity or anti-IL-1 therapy. By collecting dying monocytes after lipopolysaccharide treatment, we succeeded in enriching CIAS1-mutant monocytes and identifying low-level CIAS1-mosaicism in 3 of 4 "mutationnegative" CAPS patients. Our findings reveal a novel effect of CIAS1 mutations in promoting necrosis-like cell death, and demonstrate that CIAS1 mosaicism plays an important role in mutation-negative CAPS patients. (Blood. 2008;111: 2132-2141)

High serum levels of IL-18, KL-6, ferritin and anti-MDA5 antibodies (e.g. >200 units by ELISA) are associated with RP-ILD. These can be used as an indication for early intensive treatment. Both alveolar macrophages and autoimmunity to MDA5 are possibly involved in the development of RP-ILD associated with JDM.