Children with Coronavirus disease 2019 (COVID-19) are being reported to have manifestations of hyperinflammatory states and/or Kawasaki-like disease. In this study, we investigated children with typical and atypical Kawasaki disease (KD) likely to be associated with COVID-19. We have reported four children with Kawasaki-like disease probably associated with COVID-19. The clinical features were consistent with incomplete KD in three patients. SARS-CoV-2 RT-PCR was positive in one and the serology was positive in one patient with negative RT-PCR. Corticosteroids, anakinra, intravenous immunoglobulin (IVIG), and acetylsalicylic acid were used in the treatment. Three patients recovered after the treatment while one patient died. The literature review revealed 36 articles describing 320 children with Kawasaki-like disease associated with COVID-19. SARS-CoV-2 RT-PCR was negative in 120 (65.5%) of 183 patients while the serology was positive in 130 (83.8%) of 155 patients. The therapeutic options have included IVIG, acetylsalicylic acid, tocilizumab, anakinra, enoxaparin, and methylprednisolone. Pediatric COVID-19 cases may present with atypical/incomplete Kawasaki-like disease. Thus, pediatricians need to be aware of such atypical presentations resembling KD for early diagnosis of COVID-19.

Objective Systemic lupus erythematosus (SLE) is a chronic autoimmune disease. The ACR (American College of Rheumatology) 1997, SLICC (Systemic Lupus International Collaborating Clinics) 2012, and EULAR (European League Against Rheumatism)/ACR 2019 SLE classification criteria are formed based on data mainly from adult patients. We aimed to test the performances of the SLE classification criteria among pediatric SLE patients. Methods Pediatric SLE patients (n=262; 80.9% female) were included from three different centers in Turkey. As controls, 174 children (60.9% female) with other diseases who had ANA (antinuclear antibody) test results were included. The gold standard for SLE diagnosis was expert opinion. Results The sensitivities of the ACR 1997, SLICC 2012, and EULAR/ACR 2019 criteria were 68.7%, 95.4%, and 91.6%, respectively. The specificities of the ACR 1997, SLICC 2012, and EULAR/ACR 2019 criteria were 94.8%, 89.7%, and 88.5%, respectively. 18 SLE patients met the SLICC 2012 but not the EULAR/ACR 2019 criteria. Among these, hematologic involvement was prominent (13/18; 72.2%). Eight SLE patients fulfilled the EULAR/ACR 2019 but not the SLICC 2012 criteria. Among these, joint involvement was prominent (6/8; 75%). Conclusion This is the largest cohort study of pediatric SLE testing the performances of all three classification criteria. The SLICC 2012 criteria yielded the best sensitivity, while the ACR 1997 criteria had the best specificity. SLICC 2012 criteria performed better than EULAR/ACR 2019 criteria. Separation of different hematological manifestations in the SLICC 2012 criteria might have contributed to the higher performance of this criteria set.

Objective We aimed to describe the typical clinical and laboratory features and treatment of children diagnosed with multisystem inflammatory syndrome in children (MIS-C) and to understand the differences as compared to severe/critical pediatric cases with COVID-19 in an eastern Mediterranean country. Methods Children (aged <18 years) who diagnosed with MIS-C and severe/critical pediatric cases with COVID-19 and were admitted to hospital between March 26 and November 3, 2020 were enrolled in the study. Results A total of 52 patients, 22 patients diagnosed with COVID-19 with severe/critical disease course and 30 patients diagnosed with MIS-C, were included in the study. Although severe COVID-19 cases and cases with MIS-C share many clinical and laboratory features, MIS-C cases had longer fever duration and higher rate of the existence of rash, conjunctival injection, peripheral edema, abdominal pain, altered mental status, and myalgia than in severe cases (p<0.001 for each). Of all, 53.3% of MIS-C cases had the evidence of myocardial involvement as compared to severe cases (27.2%). Additionally, C-reactive protein (CRP) and white blood cell (WBC) are the independent predictors for the diagnosis of MIS-C, particularly in the existence of conjunctival injection and rash. Corticosteroids, intravenous immunoglobulin (IVIG), and biologic immunomodulatory treatments were mainly used in MIS-C cases rather than cases with severe disease course. There were only three deaths among 52 patients, one of whom had Burkitt lymphoma and the two cases with severe COVID-19 of late referral. Conclusion Differences between clinical presentations, acute phase responses, organ involvements, and management strategies indicate that MIS-C might be a distinct immunopathogenic disease as compared to pediatric COVID-19. Conjunctival injection and higher CRP and low WBC count are reliable diagnostic parameters for MIS-C cases. Keywords Kawasaki disease. Pediatrics. Hyperinflammation. Multisystem inflammatory syndrome in children (MIS-C). Multisystem inflammatory syndrome in adults (MIS-A) Key Points • MIS-C cases had longer fever duration and higher rate of the existence of rash, conjunctival injection, peripheral edema, abdominal pain, altered mental status, and myalgia than in severe/critical pediatric cases with COVID-19. • Higher CRP and low total WBC count are the independent predictors for the diagnosis of MIS-C. • MIS-C might be a distinct immunopathogenic disease as compared to pediatric COVID-19.

Background Coronavirus disease 19 (COVID-19) may have a severe course in children. Multisystem inflammatory syndrome in children (MIS-C) is the post-COVID complication characterized by an exaggerated inflammation, observed in children. However, data on the underlying pathophysiology are sparse. We therefore aimed to assess the cytokine and chemokine profiles of children with MIS-C and compare these to life-threatening severe SARS-CoV-2 and healthy controls (HCs) to shed light on disease pathophysiology. Methods Samples of 31 children with MIS-C, 10 with severe/critical COVID-19 and 11 HCs were included. Cytokine and chemokine profiles were studied and compared in between groups. Results Most cytokines and chemokines related to IL-1 family and IFN-γ pathway (including IL-18 and MIG/CXCL9) and IL-17A were significantly higher in the MIS-C group when compared to the severe/critical COVID-19 group and HCs. IP-10/CXCL10 and IL-10 were higher in both MIS-C patients and severe/critical COVID-19 compared to HCs. Conclusion Our results suggest that IL-1 and IFN-γ pathways play an important role in the pathophysiology of MIS-C. Impact This study defines a pattern of distinctive immune responses in children with MIS-C and in patients with severe/critical COVID-19. As the COVID-19 pandemic continues, biomarkers to identify MIS-C risk are needed to guide our management that study results may shed light on it.

Objectives FMF is a prototype of autoinflammatory diseases associated with excess IL1 production. Anti-IL1 treatments are the first-line alternatives in colchicine-resistant/intolerant FMF patients. We aimed to investigate the efficacy and safety of anti-IL1 treatment in paediatric FMF patients in our local [Hacettepe univErsity eLectronIc research fOrmS (HELIOS)] registry. Methods HELIOS is a web-based biologic drug registry for paediatric rheumatology patients. We have analysed the clinical features, disease activity parameters, treatment responses and safety outcomes in FMF patients treated with anti-IL1 agents. Results Forty paediatric FMF patients (34 continuous and six on-demand use) were included. Among the continuously treated group (61.7% female), the mean age at the start of colchicine was 5.55 (3.87) years. Age at onset of the anti-IL1 treatment was 11.47 (5.41) years with a mean follow-up duration of 3.87 (1.96) years. Apart from two, all patients had biallelic exon-10 mutations. We also gave anti-IL1 treatment on an on-demand basis in six patients. Anakinra was used as the first-line anti-IL1 treatment. During the last visit, six patients were treated with anakinra and 28 patients with canakinumab. Anti-IL1 treatment decreased the CRP levels and number and severity of the attacks. There were three hospitalizations reported due to mild infections. Eleven patients had local skin reactions, two patients had leucopenia with anakinra and one patient had thrombocytopenia with canakinumab. There was no malignancy or other severe adverse reactions. Conclusion Anakinra and canakinumab are efficient and safe alternatives in colchicine-resistant or -intolerant paediatric FMF patients. We also, for the first time, report on-demand use of anti-IL1 in paediatric FMF patients.

Objectives Multisystem inflammatory syndrome in children (MIS-C) is a rare but severe condition associated with coronavirus disease 2019 (COVID-19). Here we aimed to raise awareness for the symptoms of MIS-C in patients with rheumatic diseases, emphasizing the challenges of the differential features. Methods We retrospectively evaluated the demographic and clinical characteristics, laboratory and imaging findings, treatments, and outcomes of six MIS-C patients with previous rheumatic disease. Results Three of the patients had familial Mediterranean fever (FMF), one had juvenile dermatomyositis (JDM), one had systemic juvenile idiopathic arthritis (JIA), and another patient had oligoarticular JIA. All FMF patients presented with fever and abdominal pain, two also had chest pain. The patient with systemic JIA presented with fever, rash, and myalgia. All patients had elevated inflammatory markers and high d-dimer levels. Chest imaging of two FMF patients showed infiltrations compatible with pneumonia. One FMF patient had mildly decreased systolic functions with a shortening fraction of 48% in his echocardiography. Intravenous immunoglobulin and methylprednisolone were administered to all patients. Anakinra was given to four patients. Conclusions Clinical and laboratory signs of MIS-C may overlap with the findings of various rheumatic diseases, and this may cause a delay in diagnosis.

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Objective. Takayasu's arteritis (TAK) is a chronic vasculitis, affecting predominantly the aorta and/or its major branches. The aim of this study was to compare the differences between childhood and adult onset TAK.Methods. We retrospectively evaluated 179 TAK patients followed between August 2005 and July 2019. Demographic characteristics, laboratory features, disease activity, echocardiographic data at diagnosis and treatment regimens in the disease course were compared between the paediatric and adult onset patients. Results. Twenty-five paediatric-onset (<18 years of age at diagnosis) and 154adult-onset patients (≥18 years of age at diagnosis) were enrolled. The mean age at diagnosis for children and adults were 13.6±4 and 35.6±13, respectively. Paediatric onset TAK patients had more intense inflammation at the time of diagnosis reflected in their clinical findings. Acute phase reactants were high in all paediatric patients and significantly higher in patients with paediatric-onset TAK (p=0.006 and p=0.005, respectively). Abdominal predominant disease was more common in the paediatric group, in contrast, focal disease and aortic arch predominant disease were more common in the adult group. Ascending aortic dilatation, left ventricular hypertrophy and moderate-severe aortic insufficiency were more frequent in echocardiography findings of paediatric onset TAK patients. In comorbidities, hypertension was more common in paediatric TAK patients during followup, whereas cerebrovascular disease was more common in adult patients. Conclusion. Our paediatric onset TAKpatients presented with a more severe inflammation and more widespread vascular involvement. Multicentre studies from different geographic areas are needed to verify our observation and understand the underlying causes. Methods Study protocol and patientsWe retrospectively evaluated the medical records of TAK patients followed at