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Multisystem inflammatory syndrome in children (MIS-C) evolves in some pediatric patients following acute infection with SARS-CoV-2 by hitherto unknown mechanisms. Whereas acute-COVID-19 severity and outcomes were previously correlated with Notch4 expression on Tregs, here, we show that Tregs in MIS-C were destabilized through a Notch1-dependent mechanism. Genetic analysis revealed that patients with MIS-C had enrichment of rare deleterious variants affecting inflammation and autoimmunity pathways, including dominant-negative mutations in the Notch1 regulators NUMB and NUMBL leading to Notch1 upregulation. Notch1 signaling in Tregs induced CD22, leading to their destabilization in a mTORC1-dependent manner and to the promotion of systemic inflammation. These results identify a Notch1/CD22 signaling axis that disrupts Treg function in MIS-C and point to distinct immune checkpoints controlled by individual Treg Notch receptors that shape the inflammatory outcome in SARS-CoV-2 infection.

Background Our aim was to identify acute kidney injury (AKI) and subacute kidney injury using both KDIGO criteria and urinary biomarkers in children with mild/moderate COVID-19. Methods This cross-sectional study included 71 children who were hospitalized with a diagnosis of COVID-19 from 3 centers in Istanbul and 75 healthy children. We used a combination of functional (serum creatinine) and damage (NGAL, KIM-1, and IL-18) markers for the definition of AKI and subclinical AKI. Clinical and laboratory features were evaluated as predictors of AKI and subclinical AKI. Results Patients had significantly higher levels of urinary biomarkers and urine albumin–creatinine ratio than healthy controls ( p  < 0.001). Twelve patients (16.9%) developed AKI based on KDIGO criteria, and 22 patients (31%) had subclinical AKI. AKI group had significantly higher values of neutrophil count on admission than both subclinical AKI and non-AKI groups ( p  < 0.05 for all). Neutrophil count was independently associated with the presence of AKI ( p  = 0.014). Conclusions This study reveals that even children with a mild or moderate disease course are at risk for AKI. Association between neutrophil count and AKI may point out the role of inflammation in the development of AKI. Impact The key message of our article is that not only children with severe disease but also children with mild or moderate disease have an increased risk for kidney injury due to COVID-19. Urinary biomarkers enable the diagnosis of a significant number of patients with subclinical AKI in patients without elevation in serum creatinine. Our findings reveal that patients with high neutrophil count may be more prone to develop AKI and should be followed up carefully. We conclude that even children with mild or moderate COVID-19 disease courses should be evaluated for AKI and subclinical AKI, which may improve patient outcomes.

Background: Staphylococcus aureus is a significant pathogen causing both local and systemic infections in children, with deep tissue involvement leading to severe complications. This study aimed to assess clinical manifestations and identify risk factors for deep tissue involvement in pediatric S. aureus infections. Methods: All children between 1 month and 18 years who had S. aureus growth in blood, pus, or joint fluid culture were included. Results: A total of 61 patients (median age 55 months) were included, with 22.9% having deep tissue infections. Osteoarticular infections, pyomyositis, and pulmonary involvement were common. Deep-seated infections were significantly associated with community-acquired infections and positive hemocultures after 72 h (p < 0.01). Laboratory results showed significantly higher levels of C-reactive protein, sedimentation rate, D-dimer, and fibrinogen in the group with deep-seated infections (p = 0.02, p = 0.018, p = 0.01, and p = 0.015, respectively). The decision tree model showed that the first indicator of deep-seated infection was a D-dimer level above 1.15 mg/L, followed by a fibrinogen level above 334 mg/dL. Conclusions: Deep-seated S. aureus infections are more frequently associated with community-acquired cases, persistent hemoculture positivity, and methicillin-susceptible Staphylococcus aureus (MSSA) strains. Additionally, elevated D-dimer and fibrinogen levels may serve as valuable markers for identifying deep-seated infections in pediatric patients.

Abstract Introduction: Pulmonary exacerbations increase the requirement of aminoglycoside (AG) antibiotics in people with cystic fibrosis (pwCF). Several studies have shown that AGs have a cumulative effect on ototoxicity. We aimed to investigate the relationship between AG exposure and ototoxicity by using 3 different methods in patients with CF. Materials/Methods: The multicenter study included 121 pwCF aged between 5 and 18 years with a history of parenteral AG exposure. Standard pure-tone audiometry, extended high-frequency pure-tone audiometry (EHF-PTA), and distortion-product otoacoustic emissions (DPOAE) tests were performed. Mitochondrial mutation analysis for m1555G>A was performed in 61 patients. Results: Median age was 12.85 years and 52.1% (n = 63) were male. 18.2% (n = 22) of the patients had received parenteral AGs more than 5 courses/lifetime. Ototoxicity was detected in at least one of the tests in 56.2% (n = 68) of the patients. Only 10.7% (n = 13) of the patients had reported a symptom indicating ototoxicity. 30.3% (n = 30) of the patients had ototoxicity in the low exposure group, while it was 45.5% (n = 10) in the high exposure group according to EHF-PTA (p > 0.05). Median number of parenteral amikacin courses was significantly higher in the ototoxic group (2 [1.25–5.75] vs. 2 [1–3]; p = 0.045). No m1555A>G mutation was detected in 61 patients who screened for mitochondrial mutation analysis. Conclusion: As AG ototoxicity occurs primarily at high frequencies, EHF-PTA is important in early detecting ototoxicity. EHF-PTA and DPOAE detected ototoxicity in some patients with normal PTA results. All pwCF with a history of AG exposure should be evaluated for hearing loss since symptoms may only be noticed in the late period.

Childhood interstitial lung diseases (chILD) and immunodeficiencies are rare, heterogeneous, and clinically challenging disorders. This study aimed to evaluate the clinical and radiological characteristics of immunodeficiency-related chILD using data from the Türkiye chILD Registry (chILD-TR). We conducted a retrospective cohort study using data collected from the chILD-TR in 2023. Patients registered with the B3 code, according to the chILD-European classification, from 18 participating centers were included. Patients were classified into primary immunodeficiency (PID) and secondary immunodeficiency (SID) groups. Demographic, clinical, and radiological variables were compared between the two groups. Among 667 patients registered in the chILD-TR, 114 (17%) had immunodeficiency-related chILD, including 53 (47%) females. The median current age was 156 months (range: 23-357), the age at symptom onset was 60 months (range: 0-215), and the age at chILD diagnosis was 85 months (range: 2-217). PID was identified in 77 patients (67.6%) and SID in 37 patients (32.4%). The PID group had significantly lower median current age, age at first symptom, and age at chILD diagnosis compared with the SID group ( < 0.05). No significant differences were observed in growth z-scores between the groups ( > 0.05). A history of hematopoietic stem cell transplantation (HSCT) and a diagnosis of bronchiolitis obliterans (BO) were more frequent in the SID group ( < 0.05). The most common computed tomography findings were ground-glass opacities in PID and mosaic perfusion in SID. During follow-up, 14 patients (12.3%) died. Immunodeficiency-associated chILD encompasses a heterogeneous spectrum of disorders and is associated with increased mortality. Distinct clinical and radiological patterns were observed between PID and SID. These findings underscore the importance of early detection, individualized diagnostic strategies, and ongoing follow-up to improve outcomes in this high-risk population. Recognition of post-infectious BO and following HSCT is critical for timely intervention.