Pulmonary embolism in pediatric and adolescent patients with COVID-19 infection during the SARS-CoV-2 delta wave.

Coronavirus disease 2019 (COVID-19) infection in children has been associated with thrombosis, though few cases of COVID-associated pulmonary embolism (PE) have been described. We performed a retrospective review of the nine cases of COVID-19-associated PE during the B.1617.2 variant surge at Texas Children's Hospital. The patient cohort largely contained unvaccinated obese adolescents. All patients were critically ill with two requiring catheter-directed thrombolysis in addition to anticoagulation. Eight of the nine patients had COVID pneumonia along with PE. This report stresses the importance of maintaining a high index of suspicion for PE in pediatric COVID-19 infection and vaccinating obese adolescent patients.

Genetic and mechanistic diversity in pediatric hemophagocytic lymphohistiocytosis.

The HLH-2004 criteria are used to diagnose hemophagocytic lymphohistiocytosis (HLH), yet concern exists for their misapplication, resulting in suboptimal treatment of some patients. We sought to define the genomic spectrum and associated outcomes of a diverse cohort of children who met the HLH-2004 criteria. Genetic testing was performed clinically or through research-based whole-exome sequencing. Clinical metrics were analyzed with respect to genomic results. Of 122 subjects enrolled over the course of 17 years, 101 subjects received genetic testing. Biallelic familial HLH (fHLH) gene defects were identified in only 19 (19%) and correlated with presentation at younger than 1 year of age (P < .0001). Digenic fHLH variants were observed but lacked statistical support for disease association. In 28 (58%) of 48 subjects, research whole-exome sequencing analyses successfully identified likely molecular explanations, including underlying primary immunodeficiency diseases, dysregulated immune activation and proliferation disorders, and potentially novel genetic conditions. Two-thirds of patients identified by the HLH-2004 criteria had underlying etiologies for HLH, including genetic defects, autoimmunity, and malignancy. Overall survival was 45%, and increased mortality correlated with HLH triggered by infection or malignancy (P < .05). Differences in survival did not correlate with genetic profile or extent of therapy. HLH should be conceptualized as a phenotype of critical illness characterized by toxic activation of immune cells from different underlying mechanisms. In most patients with HLH, targeted sequencing of fHLH genes remains insufficient for identifying pathogenic mechanisms. Whole-exome sequencing, however, may identify specific therapeutic opportunities and affect hematopoietic stem cell transplantation options for these patients.

Hepatobiliary Dysfunction and Disseminated Intravascular Coagulation Increase Risk of Mortality in Pediatric Hemophagocytic Lymphohistiocytosis.

OBJECTIVES: Hemophagocytic lymphohistiocytosis poses significant challenges due to limited tools to guide clinical decisions in a population at high risk of death. We sought to assess whether disseminated intravascular coagulation and hepatobiliary dysfunction, significant comorbidities seen in critical care settings, would identify hemophagocytic lymphohistiocytosis patients with increased risk of mortality. DESIGN: Retrospective chart review. SETTING: Single-center PICU. PATIENTS: All patients admitted to a tertiary care children's hospital diagnosed with hemophagocytic lymphohistiocytosis from 2005 to 2012. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Forty-three patients were diagnosed with hemophagocytic lymphohistiocytosis with median age of 61 months. The 5-year overall survival was 51% (22/43). Univariate analyses revealed ferritin levels greater than 10,000 (ng/mL), international normalized ratio greater than 1.5, or platelet counts less than 100,000/µL at initiation of dexamethasone were individually associated with mortality. Development of disseminated intravascular coagulation, hepatobiliary dysfunction, or both increased the likelihood of death in hemophagocytic lymphohistiocytosis patients (relative risk; 95% CI) (6; 1.4-34; p < 0.05), (4.1; 1.8-10; p < 0.05), and (7.5; 1.8-42; p < 0.05). Of 12 autopsies performed, 75% had at least one active infection, 66% had chronic lymphopenia, 50% had lymphocyte depletion in the spleen, thymus, or bone marrow, 42% had evidence of microvascular thrombosis, and 92% had evidence of hepatocellular injury. CONCLUSIONS: Hemophagocytic lymphohistiocytosis continues to have high mortality with hemophagocytic lymphohistiocytosis-1994/2004 (dexamethasone/etoposide), the current standard of care for all children with hemophagocytic lymphohistiocytosis. Hemophagocytic lymphohistiocytosis patients who developed disseminated intravascular coagulation, hepatobiliary dysfunction, or both had higher risk of death with mortalities of 60%, 77%, and 77%, respectively. Phenotypic classifications are urgently needed to guide individualized treatment strategies to improve outcomes for children with hemophagocytic lymphohistiocytosis.

Implementing a Pediatric Pulmonary Embolism Response Team Model: An Institutional Experience.

Pulmonary embolism is increasing in prevalence among pediatric patients; although still rare, it can create a significant risk for morbidity and death within the pediatric patient population. Pulmonary embolism presents in various ways depending on the patient, the size of the embolism, and the comorbidities. Treatment decisions are often driven by the severity of the presentation and hemodynamic effects; severe presentations require more invasive and aggressive treatment. We describe the development and implementation of a pediatric pulmonary embolism response team designed to facilitate rapid, multidisciplinary, data-driven treatment decisions and management.

Elevated bile acids are associated with left ventricular structural changes in biliary atresia.

BACKGROUND: In children with biliary atresia (BA), pathologic structural changes within the heart, which define cirrhotic cardiomyopathy, are associated with adverse perioperative outcomes. Despite their clinical relevance, little is known about the pathogenesis and triggers of pathologic remodeling. Bile acid excess causes cardiomyopathy in experimental cirrhosis, but its role in BA is poorly understood. METHODS: Echocardiographic parameters of left ventricular (LV) geometry [LV mass (LVM), LVM indexed to height, left atrial volume indexed to BSA (LAVI), and LV internal diameter (LVID)] were correlated with circulating serum bile acid concentrations in 40 children (52% female) with BA listed for transplantation. A receiver-operating characteristic curve was generated to determine optimal threshold values of bile acids to detect pathologic changes in LV geometry using Youden index. Paraffin-embedded human heart tissue was separately analyzed by immunohistochemistry for the presence of bile acid-sensing Takeda G-protein-coupled membrane receptor type 5. RESULTS: In the cohort, 52% (21/40) of children had abnormal LV geometry; the optimal bile acid concentration to detect this abnormality with 70% sensitivity and 64% specificity was 152 µmol/L (C-statistics=0.68). Children with bile acid concentrations >152 µmol/L had ∼8-fold increased odds of detecting abnormalities in LVM, LVM index, left atrial volume index, and LV internal diameter. Serum bile acids positively correlated with LVM, LVM index, and LV internal diameter. Separately, Takeda G-protein-coupled membrane receptor type 5 protein was detected in myocardial vasculature and cardiomyocytes on immunohistochemistry. CONCLUSION: This association highlights the unique role of bile acids as one of the targetable potential triggers for myocardial structural changes in BA.

Secretion of von Willebrand Factor and Suppression of ADAMTS-13 Activity by Markedly High Concentration of Ferritin.

Hyperferritinemia is associated with poor outcomes in critically ill patients with sepsis, hemophagocytic lymphohistiocytosis (HLH), macrophage activation syndromes (MAS) and coronavirus disease 19 (COVID-19). Autopsies of hyperferritinemic patients that succumbed to either sepsis, HLH, MAS or COVID-19 have revealed disseminated microvascular thromboses with von Willebrand factor (VWF)-, platelets-, and/or fibrin-rich microthrombi. It is unknown whether high plasma ferritin concentration actively promotes microvascular thrombosis, or merely serves as a prognostic biomarker in these patients. Here, we show that secretion of VWF from human umbilical vein endothelial cells (HUVEC) is significantly enhanced by 100,000 ng/ml of recombinant ferritin heavy chain protein (FHC). Ferritin fraction that was isolated by size exclusion chromatography from the plasma of critically ill HLH patients promoted VWF secretion from HUVEC, compared to similar fraction from non-critically ill control plasma. Furthermore, recombinant FHC moderately suppressed the activity of VWF cleaving metalloprotease ADAMTS-13. These observations suggest that a state of marked hyperferritinemia could promote thrombosis and organ injury by inducing endothelial VWF secretion and reducing the ADAMTS-13 activity.

Role of Damage-Associated Molecular Patterns and Uncontrolled Inflammation in Pediatric Sepsis-Induced Multiple Organ Dysfunction Syndrome.

The incidence of multiple organ dysfunction syndrome (MODS) in sepsis varies from 17 to 73% and furthermore, increases the risk of death by 60% when controlled for the number of dysfunctional organs. Several MODS phenotypes exist, each unique in presentation and pathophysiology. Common to the phenotypes is the stimulation of the immune response by pathogen-associated molecular patterns (PAMPs), or danger-associated molecular patterns (DAMPs) causing an unremitting inflammation. Two of the MODS phenotypes are discussed in detail, thrombocytopenia-associated multiple organ failure (TAMOF) and the hyperinflammatory phenotype-macrophage activating syndrome (MAS) and hemophagocytic lymphohistiocytosis (HLH). In the end, we will briefly review the role of mitochondrial dysfunction as a significant contributor to the pathogenesis of MODS.