Multisystem inflammatory syndrome in children (MIS-C) is a rare and severe condition that follows benign COVID-19. We report autosomal recessive deficiencies of OAS1 , OAS2 , or RNASEL in five unrelated children with MIS-C. The cytosolic dsRNA-sensing OAS1 and OAS2 generate 2′-5′-linked oligoadenylates (2-5A) that activate the ssRNA-degrading RNase L. Monocytic cell lines and primary myeloid cells with OAS1 , OAS2 , or RNASEL deficiencies produce excessive amounts of inflammatory cytokines upon dsRNA or SARS-CoV-2 stimulation. Exogenous 2-5A suppresses cytokine production in OAS1- but not RNase L-deficient cells. Cytokine production in RNase L-deficient cells is impaired by MDA5 or RIG-I deficiency and abolished by MAVS deficiency. Recessive OAS–RNase L deficiencies in these patients unleash the production of SARS-CoV-2–triggered, MAVS-mediated inflammatory cytokines by mononuclear phagocytes, thereby underlying MIS-C.

Pediatrics multisystem inflammatory syndrome (PMIS) is an inflammatory condition in children, which usually involves fever and multiple organ failure associated with COVID-19. The condition may match some or all of the diagnostic criteria for Kawasaki disease (KD). 1 PMIS usually develops 1 month later in patients after the first exposure of acute COVID-19. The pathogenesis of PMIS was illness mediated by acquired immunity rather than direct viral injury. The antibody tests were positive in the cases with PMIS, but the results of COVID-19 polymerase chain reaction (PCR) were negative in most of the cases. According to the literature, PMIS has four different clinical presentations from Kawasaki-like illness syndrome to refractory vasodilatory shock (toxic shock syndrome like). 2-5 Thus, due to all of these differ

Multisystemic inflammatory syndrome (MIS-C) diagnosis remains difficult because the clinical features overlap with Kawasaki disease (KD). The study aims to highlight the clinical and laboratory features and outcomes of patients with MISC whose clinical manifestations overlap with or without KD. This study is a retrospective analysis of a case series designed for patients aged 1 month to 18 years in 28 hospitals between November 1, 2020, and June 9, 2021. Patient demographics, complaints, laboratory results, echocardiographic results, system involvement, and outcomes were recorded. A total of 614 patients were enrolled; the median age was 7.4 years (interquartile range (IQR) 3.9–12 years). A total of 277 (45.1%) patients with MIS-C had manifestations that overlapped with KD, including 92 (33.3%) patients with complete KD and 185 (66.7%) with incomplete KD. Lymphocyte and platelet counts were significantly lower in patients with MISC, overlapped with KD (lymphocyte count 1080 vs. 1280 cells × μL, p = 0.028; platelet count 166 vs. 216 cells × 10 3 /μL, p < 0.001). The median serum procalcitonin levels were statistically higher in patients overlapped with KD (3.18 vs. 1.68 µg/L, p = 0.001). Coronary artery dilatation was statistically significant in patients with overlap with KD (13.4% vs. 6.8%, p = 0.007), while myocarditis was significantly more common in patients without overlap with KD features (2.6% vs 7.4%, p = 0.009). The association between clinical and laboratory findings and overlap with KD was investigated. Age > 12 years reduced the risk of overlap with KD by 66% ( p < 0.001, 95% CI 0.217–0.550), lethargy increased the risk of overlap with KD by 2.6-fold ( p = 0.011, 95% CI 1.244–5.439), and each unit more albumin (g/dl) reduced the risk of overlap with KD by 60% ( p < 0.001, 95% CI 0.298–0.559). Conclusion : Almost half of the patients with MISC had clinical features that overlapped with KD; in particular, incomplete KD was present. The median age was lower in patients with KD-like features. Lymphocyte and platelet counts were lower, and ferritin and procalcitonin levels were significantly higher in patients with overlap with KD. What is Known: • In some cases of MIS-C, the clinical symptoms overlap with Kawasaki disease. • Compared to Kawasaki disease, lymphopenia was an independent predictor of MIS-C. What is New: • Half of the patients had clinical features that overlapped with Kawasaki disease. • In patients whose clinical features overlapped with KD, procalcitonin levels were almost 15 times higher than normal. • Lethargy increased the risk of overlap with KD by 2.6-fold in MIS-C pa...

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Aim We aimed to assess the impact of COVID‐19 on asthma exacerbations and to compare the severity of symptoms of SARS‐CoV‐2 infection of asthmatic children with those of healthy children. Methods The clinical course of COVID‐19 was compared among 89 children with asthma and 84 healthy children with age‐ and gender‐matched. Demographic factors, severity of asthma, duration of asthma, presence of atopy, type of treatment, and compliance to treatment in asthmatic children on clinical course of infection and to determine the risk factors for severe course for asthma exacerbation during COVID‐19 were evaluated retrospectively. Demographic characteristics, clinical symptoms, duration of complaints, and hospitalization rates were statistically compared between the two groups. Results Both groups had similar rates of symptomatic disease, hospitalization, and duration of fever. Among children with asthma mean age was 10.3 years, 59.6% were male, and 84.3% had mild asthma. Dyspnea was more prevalent in asthmatic children ( p :0.012), but other clinical findings were not different from those of healthy controls. 12.4% ( n :11) of asthmatic children had asthma exacerbation, 2.2% ( n :2) of them were hospitalized; one (1.1%) of which was due to asthma exacerbation. Conclusion The course of COVID‐19 in patients with mild to moderate asthma, who were followed up regularly and who were compliant with their treatment, was similar to their healthy peers. Since there was no severe asthma case in our study, the results could not have been generalized to all asthmatic patients. Further comprehensive and multicenter studies are required in pediatric population.