Defining criteria for disease activity states in juvenile dermatomyositis based on the Juvenile Dermatomyositis Activity Index.

OBJECTIVES: To develop and validate the cut-offs in the Juvenile DermatoMyositis Activity Index (JDMAI) to distinguish the states of inactive disease (ID), low disease activity (LDA), moderate disease activity (MDA) and high disease activity (HDA) in children with juvenile dermatomyositis (JDM). METHODS: For cut-off definition, data from 139 patients included in a randomised clinical trial were used. Among the six versions of the JDMAI, JDMA1 (score range 0-40) and JDMAI2 (score range 0-39) were selected. Optimal cut-offs were determined against external criteria by calculating different percentiles of score distribution and through receiver operating characteristic curve analysis. External criteria included the modified Pediatric Rheumatology International Trials Organization (PRINTO) criteria for clinically ID in JDM (for ID) and PRINTO levels of improvement in the clinical trial (for LDA and HDA). MDA cut-offs were set at the score interval between LDA and HDA cut-offs. Cut-off validation was conducted by assessing construct and discriminative ability in two cohorts including a total of 488 JDM patients. RESULTS: The calculated JDMAI1 cut-offs were ≤2.4 for ID, ≤6.6 for LDA, 6.7-11 for MDA and >11 for HDA. The calculated JDMAI2 cut-offs were ≤5.2 for ID, ≤8.5 for LDA, 8.6-11.3 for MDA and >11.3 for HDA. The cut-offs discriminated strongly among disease activity states defined subjectively by caring physicians and parents, parents' satisfaction or non-satisfaction with illness outcome, levels of pain, fatigue, physical functional impairment and physical well-being. CONCLUSIONS: Both JDMAI1 and JDMAI2 cut-offs revealed good metrologic properties in validation analyses and are, therefore, suited for application in clinical practice and research.

Patterns and determinants of response to novel therapies in juvenile and adult-onset polyarthritis.

Biologic and targeted synthetic DMARDs (b/tsDMARDs) have revolutionized the management of multiple rheumatic inflammatory conditions. Among these, polyarticular JIA (pJIA) and RA display similarities in terms of disease pathophysiology and response pattern to b/tsDMARDs. Indeed, the therapeutic efficacy of novel targeted drugs is variable among individual patients, in both RA and pJIA. The mechanisms and determinants of this heterogeneous response are diverse and complex, such that the development of true 'precision'-medicine strategies has proven highly challenging. In this review, we will discuss pathophysiological, patient-specific, drug-specific and environmental factors contributing to individual therapeutic response in pJIA in comparison with what is known in RA. Although some biomarkers have been identified that stratify with respect to the likelihood of either therapeutic response or non-response, few have proved useful in clinical practice so far, likely due to the complexity of treatment-response mechanisms. Consequently, we propose a pragmatic, patient-centred and clinically based approach, i.e. personalized instead of biomarker-based precision medicine in JIA.

Curation and expansion of the Human Phenotype Ontology for systemic autoinflammatory diseases improves phenotype-driven disease-matching.

Introduction: Accurate and standardized phenotypic descriptions are essential in diagnosing rare diseases and discovering new diseases, and the Human Phenotype Ontology (HPO) system was developed to provide a rich collection of hierarchical phenotypic descriptions. However, although the HPO terms for inborn errors of immunity have been improved and curated, it has not been investigated whether this curation improves the diagnosis of systemic autoinflammatory disease (SAID) patients. Here, we aimed to study if improved HPO annotation for SAIDs enhanced SAID identification and to demonstrate the potential of phenotype-driven genome diagnostics using curated HPO terms for SAIDs. Methods: We collected HPO terms from 98 genetically confirmed SAID patients across eight different European SAID expertise centers and used the LIRICAL (Likelihood Ratio Interpretation of Clinical Abnormalities) computational algorithm to estimate the effect of HPO curation on the prioritization of the correct SAID for each patient. Results: Our results show that the percentage of correct diagnoses increased from 66% to 86% and that the number of diagnoses with the highest ranking increased from 38 to 45. In a further pilot study, curation also improved HPO-based whole-exome sequencing (WES) analysis, diagnosing 10/12 patients before and 12/12 after curation. In addition, the average number of candidate diseases that needed to be interpreted decreased from 35 to 2. Discussion: This study demonstrates that curation of HPO terms can increase identification of the correct diagnosis, emphasizing the high potential of HPO-based genome diagnostics for SAIDs.

Biallelic mutations in the CFHR genes underlying atypical hemolytic uremic syndrome in a patient with catastrophic adult-onset Still's disease and recurrent macrophage activation syndrome: A case report.

We report the fatal case of a 20-year-old woman with refractory adult-onset Still's disease (AOSD) accompanied by fulminant macrophage activation syndrome (MAS) and atypical hemolytic uremic syndrome (aHUS). Anakinra and tocilizumab temporarily controlled AOSD. In 2021, she presented to ICU with generalized tonic-clonic seizure, lymphocytic aseptic meningitis, and acute kidney injury. Despite hemodialysis and methylprednisolone, she developed another seizure, MAS, and disseminated intravascular coagulation (DIC). Following brief control, MAS flares -reflected by increased plasma CXCL9 and CXCL10- re-emerged and were controlled through dexamethasone, etoposide, cyclosporin and tofacitinib. No mutations were detected in haemophagocytic lymphohistiocytosis (HLH)-associated genes, nor in genes associated with periodic fever syndromes. Post-mortem genetic testing revealed loss-of-function biallelic deletions in complement factor H-related proteins (CFHR) genes, predisposing aHUS. This case underscores the importance of prompt genetic assessment of complement-encoding alleles, in addition to HLH-related genes, in patients with severe AOSD with recurrent MAS and features of thrombotic microangiopathy (TMA).

Long-Term Maintenance of Clinical Responses by Individual Patients With Polyarticular-Course Juvenile Idiopathic Arthritis Treated With Abatacept.

OBJECTIVE: To investigate the frequency and trajectories of individual patients with polyarticular-course juvenile idiopathic arthritis (JIA) achieving novel composite end points on abatacept. METHODS: Data from a clinical trial of subcutaneous abatacept (NCT01844518) and a post hoc analysis of intravenous abatacept (NCT00095173) in patients with polyarticular-course JIA were included. Three end points were defined and evaluated: combined occurrence of low disease activity (LDA) measured by the Juvenile Arthritis Disease Activity Score; 50% improvement in American College of Rheumatology criteria for JIA (ACR50); and patient-reported outcomes. Patient-reported outcomes included visual analog scale score of minimal pain (pain-min) and Childhood Health Assessment Questionnaire disability index score of 0 (C-HAQ DI0). In this post hoc analysis, maintenance of month 13 and 21 end points (LDA+pain-min, LDA+C-HAQ DI0, and ACR50+pain-min) in those who achieved them at month 4 was determined. RESULTS: Composite end points (LDA+pain-min, LDA+C-HAQ DI0, and ACR50+pain-min) were achieved at month 4 (44.7%, 19.6%, and 58.9% of the 219 patients treated with subcutaneous abatacept, respectively). Of those who achieved LDA+pain-min at month 4, 84.7% (83 of 98) and 65.3% (64 of 98) maintained LDA+pain-min at months 13 and 21, respectively. The proportions of patients meeting LDA+pain-min outcomes increased from 44.7% (98 of 219) at month 4 to 54.8% (120 of 219) at month 21. The frequency of patients who met an LDA+C-HAQ DI score of 0 increased from 19.6% (43 of 219) at month 4 to 28.8% (63 of 219) at month 21. CONCLUSION: Among individual patients with polyarticular-course JIA treated with abatacept who achieved 1 of the combined clinical and patient-reported outcomes composite end points, many maintained them over 21 months of abatacept treatment.

Factors associated with poor prognosis of hip arthritis in juvenile idiopathic arthritis: Data from the JIR cohort.

OBJECTIVES: Hip involvement remains a predictor of severe juvenile idiopathic arthritis (JIA) course and carries a high risk of disability. This study aims to determine the factors of poor prognosis of hip involvement in patients with JIA and to assess the treatment response. METHODS: This is a multicenter observational cohort study. Patients were selected from the JIR Cohort database. Hip involvement was defined as clinically suspected and confirmed by an imaging tool. Follow-up data were collected during 5 years. RESULTS: Among the 2223 patients with JIA, 341(15%) patients had hip arthritis. Male gender, enthesitis-related arthritis, and North African origin were factors associated with hip arthritis. Hip inflammation was associated with disease activity parameters during the first year, particularly Physician Global Assessment, joint count, and inflammatory marks. Structural hip progression was associated with early onset of the disease, a longer time to diagnosis, geographic origin, and JIA subtypes. Anti-TNF therapy was found to be the only treatment able to effectively reduce structural damage progression. CONCLUSION: The early onset diagnostic delay, origin, and systemic subtype of JIA predict a poor prognosis of hip arthritis in children with JIA. The use of anti-TNF was associated with a better structural prognosis.

COVID-19-related anxiety trajectories in children, young people and adults with rheumatic diseases.

Objectives: Uncertainty regarding the risk of coronavirus disease 2019 (COVID-19), its complications and the safety of immunosuppressive therapies may drive anxiety among adults and parents of children and young people (CYP) with rheumatic diseases. This study explored trajectories of COVID-related anxiety in adults and parents of CYP with rheumatic diseases. Methods: Adults and parents of CYP participating in the international COVID-19 European Patient Registry were included in the current study if they had enrolled in the 4 weeks following 24 March 2020. COVID-related anxiety scores (0-10) were collected weekly for up to 28 weeks.Group-based trajectory models explored COVID-related anxiety clusters in adult and parent populations, with optimal models chosen based on model fit, parsimony and clinical plausibility. Demographic, clinical and COVID-19 mitigation behaviours were compared between identified clusters using univariable statistics. Results: In 498 parents of CYP and 2640 adults, four common trajectory groups of COVID-related anxiety were identified in each cohort: persistent extreme anxiety (32% and 17%), persistent high anxiety (43% and 41%), improving high anxiety (25% and 32%) and improving moderate anxiety (11% and 10%), respectively. Few characteristics distinguished the clusters in the parent cohort. Higher and more persistent anxiety clusters in the adult cohort were associated with higher levels of respiratory comorbidities, use of immunosuppressive therapies, older age and greater self-isolation. Conclusions: COVID-19-related anxiety in the rheumatic disease community was high and persistent during the COVID-19 pandemic, with four common patterns identified. In the adult cohort, higher COVID-related anxiety was related to perceived risk factors for COVID-19 morbidity and mortality.

Novel method to quantify peptidylarginine deiminase activity shows distinct citrullination patterns in rheumatoid and juvenile idiopathic arthritis.

Introduction: Peptidylarginine deiminases (PADs) mediate citrullination, an irreversible posttranslational modification that converts arginine to citrulline residues in proteins. Rheumatoid arthritis (RA) is characterized by unique autoantibodies that recognize citrullinated peptides, which are highly specific for this disease. However, the mechanism preceding the anti-citrulline response remains largely unclear. PAD enzymes are known to fuel the autoimmune response by generating autoreactive epitopes, and sustain local synovial inflammation through neutrophil extracellular trap formation. Therefore, detecting endogenous PAD activity is important to understand the pathogenesis of arthritis. Methods: In this study, we improved a fluorescent in vitro assay to enable endogenous PAD activity characterization in complex samples. We combine the use of an in-house synthetic, arginine-rich substrate and a negatively charged dye molecule to visualize enzyme activity. Results: This pioneering PAD assay allowed profiling of active citrullination in leukocytes and in local and systemic samples of an arthritis cohort. Our results reveal that RA and juvenile idiopathic arthritis (JIA) synovial fluids display similar levels of PAD activity. In contrast, citrullination was limited in joints of patients suffering from gout or Lyme's disease. Interestingly, in blood, a higher level of extracellular citrullination was only found in anti-CCP-positive RA patients. Discussion: Our finding suggests that enhanced synovial PAD activity drives the loss in tolerance towards citrullinated proteins and that systemic citrullination may indicate the risk for developing citrulline-specific autoimmunity.

Dry synovitis, a rare entity distinct from juvenile idiopathic arthritis.

BACKGROUND: Dry synovitis (DS) is a rare entity as only a few cases have been reported to date. We describe the clinical features, radiological manifestations and course of DS in comparison with rheumatoid factor negative polyarticular juvenile idiopathic arthritis (RFneg-polyJIA). METHODS: We performed a multicenter retrospective collection of data of DS patients who presented with progressive joint limitations without palpable synovitis, absence of elevated acute phase reactants, negative ANA and RF, and imaging showing joint and/or osteochondral involvement. For comparative purposes, we included a cohort of RF neg-polyJIA patients. RESULTS: Twelve DS patients, 8F/4 M, with mean age at onset of 6.1 years, were included. Presenting signs comprised delayed motor development, functional limitations and/or progressive stiffness. Clinical examination showed symmetric polyarticular involvement with variable muscular atrophy. MRI showed mild, diffuse synovial involvement, without effusion. With time, signs of progressive osteochondral damage became evident, despite treatment. All patients were treated with low-dose corticosteroids and methotrexate. Anti-TNF agents were prescribed in five. The response was variable with limited joint mobility in 11/12, and need of joint replacement in 2. In comparison with a cohort of RFneg-polyJIA, DS patients presented higher number of joint involved (p = 0.0001) and contractures (p = 0.0001), less swelling (p = 0.0001) and prolonged diagnostic delay (p = 0.0001). CONCLUSION: DS represents a unique juvenile-onset arthropathy, distinct from polyarticular JIA. Awareness among pediatricians is essential for early recognition and proper treatment. Further studies, including synovial pathology, immunology and genetics may contribute to a better understanding of this rare disorder of childhood.

Multinucleation resets human macrophages for specialized functions at the expense of their identity.

Macrophages undergo plasma membrane fusion and cell multinucleation to form multinucleated giant cells (MGCs) such as osteoclasts in bone, Langhans giant cells (LGCs) as part of granulomas or foreign-body giant cells (FBGCs) in reaction to exogenous material. How multinucleation per se contributes to functional specialization of mature mononuclear macrophages remains poorly understood in humans. Here, we integrate comparative transcriptomics with functional assays in purified mature mononuclear and multinucleated human osteoclasts, LGCs and FBGCs. Strikingly, in all three types of MGCs, multinucleation causes a pronounced downregulation of macrophage identity. We show enhanced lysosome-mediated intracellular iron homeostasis promoting MGC formation. The transition from mononuclear to multinuclear state is accompanied by cell specialization specific to each polykaryon. Enhanced phagocytic and mitochondrial function associate with FBGCs and osteoclasts, respectively. Moreover, human LGCs preferentially express B7-H3 (CD276) and can form granuloma-like clusters in vitro, suggesting that their multinucleation potentiates T cell activation. These findings demonstrate how cell-cell fusion and multinucleation reset human macrophage identity as part of an advanced maturation step that confers MGC-specific functionality.

EULAR/PRES recommendations for vaccination of paediatric patients with autoimmune inflammatory rheumatic diseases: update 2021.

OBJECTIVES: Recent insights supporting the safety of live-attenuated vaccines and novel studies on the immunogenicity of vaccinations in the era of biological disease-modifying antirheumatic drugs in paediatric patients with autoimmune/inflammatory rheumatic diseases (pedAIIRD) necessitated updating the EULAR recommendations. METHODS: Recommendations were developed using the EULAR standard operating procedures. Two international expert committees were formed to update the vaccination recommendations for both paediatric and adult patients with AIIRD. After a systematic literature review, separate recommendations were formulated for paediatric and adult patients. For pedAIIRD, six overarching principles and seven recommendations were formulated and provided with the level of evidence, strength of recommendation and Task Force level of agreement. RESULTS: In general, the National Immunisation Programmes (NIP) should be followed and assessed yearly by the treating specialist. If possible, vaccinations should be administered prior to immunosuppressive drugs, but necessary treatment should never be postponed. Non-live vaccines can be safely given to immunosuppressed pedAIIRD patients. Mainly, seroprotection is preserved in patients receiving vaccinations on immunosuppression, except for high-dose glucocorticoids and B-cell depleting therapies. Live-attenuated vaccines should be avoided in immunosuppressed patients. However, it is safe to administer the measles-mumps-rubella booster and varicella zoster virus vaccine to immunosuppressed patients under specific conditions. In addition to the NIP, the non-live seasonal influenza vaccination should be strongly considered for immunosuppressed pedAIIRD patients. CONCLUSIONS: These recommendations are intended for paediatricians, paediatric rheumatologists, national immunisation agencies, general practitioners, patients and national rheumatology societies to attain safe and effective vaccination and optimal infection prevention in immunocompromised pedAIIRD patients.

Modulation of thromboinflammation in hospitalized COVID-19 patients with aprotinin, low molecular weight heparin, and anakinra: The DAWn-Antico study.

Background: Thromboinflammation plays a central role in severe COVID-19. The kallikrein pathway activates both inflammatory pathways and contact-mediated coagulation. We investigated if modulation of the thromboinflammatory response improves outcomes in hospitalized COVID-19 patients. Methods: In this multicenter open-label randomized clinical trial (EudraCT 2020-001739-28), patients hospitalized with COVID-19 were 1:2 randomized to receive standard of care (SOC) or SOC plus study intervention. The intervention consisted of aprotinin (2,000,000 IE IV four times daily) combined with low molecular weight heparin (LMWH; SC 50 IU/kg twice daily on the ward, 75 IU/kg twice daily in intensive care). Additionally, patients with predefined hyperinflammation received the interleukin-1 receptor antagonist anakinra (100 mg IV four times daily). The primary outcome was time to a sustained 2-point improvement on the 7-point World Health Organization ordinal scale for clinical status, or discharge. Findings: Between 24 June 2020 and 1 February 2021, 105 patients were randomized, and 102 patients were included in the full analysis set (intervention N = 67 vs. SOC N = 35). Twenty-five patients from the intervention group (37%) received anakinra. The intervention did not affect the primary outcome (HR 0.77 [CI 0.50-1.19], p = 0.24) or mortality (intervention n = 3 [4.6%] vs. SOC n = 2 [5.7%], HR 0.82 [CI 0.14-4.94], p = 0.83). There was one treatment-related adverse event in the intervention group (hematuria, 1.49%). There was one thrombotic event in the intervention group (1.49%) and one in the SOC group (2.86%), but no major bleeding. Conclusions: In hospitalized COVID-19 patients, modulation of thromboinflammation with high-dose aprotinin and LMWH with or without anakinra did not improve outcome in patients with moderate to severe COVID-19.

Steroid hormone catabolites activate the pyrin inflammasome through a non-canonical mechanism.

The pyrin inflammasome acts as a guard of RhoA GTPases and is central to immune defenses against RhoA-manipulating pathogens. Pyrin activation proceeds in two steps. Yet, the second step is still poorly understood. Using cells constitutively activated for the pyrin step 1, a chemical screen identifies etiocholanolone and pregnanolone, two catabolites of testosterone and progesterone, acting at low concentrations as specific step 2 activators. High concentrations of these metabolites fully and rapidly activate pyrin, in a human specific, B30.2 domain-dependent manner and without inhibiting RhoA. Mutations in MEFV, encoding pyrin, cause two distinct autoinflammatory diseases pyrin-associated autoinflammation with neutrophilic dermatosis (PAAND) and familial Mediterranean fever (FMF). Monocytes from PAAND patients, and to a lower extent from FMF patients, display increased responses to these metabolites. This study identifies an unconventional pyrin activation mechanism, indicates that endogenous steroid catabolites can drive autoinflammation, through the pyrin inflammasome, and explains the "steroid fever" described in the late 1950s upon steroid injection in humans.

Severe COVID-19 patients display hyper-activated NK cells and NK cell-platelet aggregates.

COVID-19 is characterised by a broad spectrum of clinical and pathological features. Natural killer (NK) cells play an important role in innate immune responses to viral infections. Here, we analysed the phenotype and activity of NK cells in the blood of COVID-19 patients using flow cytometry, single-cell RNA-sequencing (scRNA-seq), and a cytotoxic killing assay. In the plasma of patients, we quantified the main cytokines and chemokines. Our cohort comprises COVID-19 patients hospitalised in a low-care ward unit (WARD), patients with severe COVID-19 disease symptoms hospitalised in intensive care units (ICU), and post-COVID-19 patients, who were discharged from hospital six weeks earlier. NK cells from hospitalised COVID-19 patients displayed an activated phenotype with substantial differences between WARD and ICU patients and the timing when samples were taken post-onset of symptoms. While NK cells from COVID-19 patients at an early stage of infection showed increased expression of the cytotoxic molecules perforin and granzyme A and B, NK cells from patients at later stages of COVID-19 presented enhanced levels of IFN-γ and TNF-α which were measured ex vivo in the absence of usual in vitro stimulation. These activated NK cells were phenotyped as CD49a+CD69a+CD107a+ cells, and their emergence in patients correlated to the number of neutrophils, and plasma IL-15, a key cytokine in NK cell activation. Despite lower amounts of cytotoxic molecules in NK cells of patients with severe symptoms, majority of COVID-19 patients displayed a normal cytotoxic killing of Raji tumour target cells. In vitro stimulation of patients blood cells by IL-12+IL-18 revealed a defective IFN-γ production in NK cells of ICU patients only, indicative of an exhausted phenotype. ScRNA-seq revealed, predominantly in patients with severe COVID-19 disease symptoms, the emergence of an NK cell subset with a platelet gene signature that we identified by flow and imaging cytometry as aggregates of NK cells with CD42a+CD62P+ activated platelets. Post-COVID-19 patients show slow recovery of NK cell frequencies and phenotype. Our study points to substantial changes in NK cell phenotype during COVID-19 disease and forms a basis to explore the contribution of platelet-NK cell aggregates to antiviral immunity against SARS-CoV-2 and disease pathology.

Efficacy, Immunogenicity and Safety of Vaccination in Pediatric Patients With Autoimmune Inflammatory Rheumatic Diseases (pedAIIRD): A Systematic Literature Review for the 2021 Update of the EULAR/PRES Recommendations.

Background: In 2011, the first European League Against Rheumatism (EULAR) vaccination recommendations for pediatric patients with autoimmune inflammatory rheumatic diseases (pedAIIRD) were published. The past decade numerous new studies were performed to assess the safety, efficacy and immunogenicity of vaccinations in pedAIIRD. A systematic literature review (SLR) was therefore performed to serve as the basis for the updated 2021 EULAR/PRES recommendations. Methods: An SLR was performed according to the standard operating procedures for EULAR-endorsed recommendations. Primary outcomes were efficacy, immunogenicity and safety of vaccination in pedAIIRD. The search was performed in Medline, Embase and the Cochrane Library and included studies published from November 2010 until July 2020. Results: The SLR yielded 57 studies which were included for critical appraisal and data extraction. Only 8 studies described the occurrence of vaccine-preventable infections after vaccination (efficacy), none of these studies were powered to assess efficacy. The majority of studies assessed (humoral) immune responses as surrogate endpoint for vaccine efficacy. Studies on non-live vaccines showed that these were safe and in general immunogenic. Biologic disease-modifying antirheumatic drugs (bDMARDs) in general did not significantly reduce seroprotection rates, except for B-cell depleting therapies which severely hampered humoral responses. Four new studies on human papilloma virus vaccination showed that this vaccine was safe and immunogenic in pedAIIRD. Regarding live-attenuated vaccinations, level 1 evidence of the measles mumps rubella (MMR) booster vaccination became available which showed the safety of this booster for patients treated with methotrexate. In addition, level 3 evidence became available that suggested that the MMR and varicella zoster virus (VZV) vaccination for patients on low dose glucocorticosteroids and bDMARDs might be safe as well. Conclusions: The past decade, knowledge on the safety and immunogenicity of (live-attenuated) vaccines in pedAIIRD significantly increased. Data on efficacy (infection prevention) remains scarce. The results from this SLR are the basis for the updated EULAR/PRES vaccination recommendations in pedAIIRD.

Chronic nonbacterial osteomyelitis in children: a multicentre Belgian cohort of 30 children.

BACKGROUND: To evaluate clinical characteristics, imaging findings, therapeutic approach and outcome of paediatric patients with Chronic Non-Bacterial Osteomyelitis (CNO). METHODS: Retrospective review of 30 children diagnosed with CNO at two tertiary care centres in Belgium. Imaging data were evaluated by blinded paediatric radiologists. RESULTS: Mean age at onset was 10.3 years and mean age at diagnosis was 11.7 years. Bone pain was the leading symptom (29/30 patients). Out of 180 symptomatic lesions, 131 were confirmed on MRI as hyperintense geographic lesions on STIR images at the metaphysis and epiphysis adjacent to growth plates of tubular bones. The most common sites of involvement were the lower limbs, spine, sternoclavicular joint and humerus. For nearly half of the patients (14/30) monotherapy with NSAIDs was sufficient to obtain remission. The remaining 16 patients received second-line therapy: bisphosphonates (n = 15/30), disease-modifying antirheumatic drugs (n = 7/30), etanercept (n = 4/30) and tocilizumab (n = 1/30). Remission was reached after a mean time of 37.6 months in 26/30 patients. The prognosis was worse for patients with spinal involvement, resulting in more long-term sequelae. CONCLUSIONS: We present a multicentre paediatric cohort of 30 CNO patients. A typical pattern of bone involvement could be found on MRI. NSAIDs were administered as first-line treatment. Second-line strategies included bisphosphonates, corticosteroids, methotrexate, etanercept and tocilizumab. TRIAL REGISTRATION: Retrospectively registered. Registratienummer EC KUL: MP018023.

Human OTULIN haploinsufficiency impairs cell-intrinsic immunity to staphylococcal α-toxin.

The molecular basis of interindividual clinical variability upon infection with Staphylococcus aureus is unclear. We describe patients with haploinsufficiency for the linear deubiquitinase OTULIN, encoded by a gene on chromosome 5p. Patients suffer from episodes of life-threatening necrosis, typically triggered by S. aureus infection. The disorder is phenocopied in patients with the 5p- (Cri-du-Chat) chromosomal deletion syndrome. OTULIN haploinsufficiency causes an accumulation of linear ubiquitin in dermal fibroblasts, but tumor necrosis factor receptor-mediated nuclear factor κB signaling remains intact. Blood leukocyte subsets are unaffected. The OTULIN-dependent accumulation of caveolin-1 in dermal fibroblasts, but not leukocytes, facilitates the cytotoxic damage inflicted by the staphylococcal virulence factor α-toxin. Naturally elicited antibodies against α-toxin contribute to incomplete clinical penetrance. Human OTULIN haploinsufficiency underlies life-threatening staphylococcal disease by disrupting cell-intrinsic immunity to α-toxin in nonleukocytic cells.