Activated CD8 T-cell Hepatitis in Children With Indeterminate Acute Liver Failure: Results From a Multicenter Cohort

Characteristic immune cell interactions in livers of children with acute hepatitis revealed by spatial single-cell analysis identify a possible postacute sequel of COVID-19

BACKGROUND

A rise in paediatric cases of acute hepatitis of unknown origin (AHUO) was observed in 2022, some requiring liver transplantation. A link to adeno-associated virus 2 infection and CD4+T-cell mediated disease was reported in cohorts in the UK and USA but does not explain all cases.

OBJECTIVE

To determine the intrahepatic immune cell interactions in the inflamed liver and a possible contribution of SARS-CoV-2 infection.

DESIGN

Patients with acute non-A non-E hepatitis (10/12 AHUO, 2/12 subacute) during February 2022-December 2022 undergoing liver biopsy were recruited in a European patient cohort. Hepatological, virological, histopathological and highly multiplexed spatial and single-cell analyses of liver biopsies were performed.

RESULTS

Patients were negative for adenoviral and SARS-CoV-2 PCR. Three patients had a positive adenoviral serology and 10/12 patients had a history or serological evidence of SARS-CoV-2 infection. Imaging mass cytometry identified significant intrahepatic immune infiltration with an enrichment of CD8+T-cells. The highest CD8 infiltration and concomitant peripheral immune activation were observed in patients with the most severe hepatitis. CD8+T-cell infiltration was connected to histomorphological interface hepatitis and bridging necrosis. Cellular neighbourhood analysis indicated disease-associated microanatomic interactions between CX3CR1+ endothelial and myeloid cell populations, interacting with effector CD8+T-cells suggesting a pathogenic cellular triad. Of note, we detected intrahepatic SARS-CoV-2 antigens in ACE2-expressing cells in the areas with significant pathology in 11/12 samples using several different detection methods. 10/12 patients were treated with corticosteroid therapy and no liver transplantation was required.

CONCLUSIONS

We identified a possible manifestation of an immune-mediated postacute sequel to COVID-19 associated with a characteristic immune infiltrate in children with AHUO. COVID-19 testing should be considered in paediatric AHUO.

Origins of T-cell-mediated autoimmunity in acquired aplastic anaemia

Acquired aplastic anaemia (AA) is an autoimmune bone marrow failure disease resulting from a cytotoxic T-cell-mediated attack on haematopoietic stem and progenitor cells (HSPCs). Despite significant progress in understanding the T-cell repertoire alterations in AA, identifying specific pathogenic T cells in AA patients has remained elusive, primarily due to the unknown antigenic targets of the autoimmune attack. In this review, we will synthesize findings from several decades of research to critically evaluate the current knowledge on T-cell repertoires in AA. We will highlight new insights gained from recent in vitro studies of candidate autoreactive T cells isolated from AA patients and will discuss efforts to identify shared T-cell clonotypes in AA. Finally, we will discuss emerging evidence on the potential T-cell cross-reactivity between HSPC and common viral epitopes that may contribute to the development of AA in some patients. We conclude by highlighting the areas of consensus and limitations, as well as the ongoing uncertainties, and we identify promising directions for future research in the field.

Efficacy of steroid therapy for improving native liver survival after pediatric acute liver failure with immune activation

AIM

Recent evidence suggests that acute liver failure (ALF) in some patients may reflect a dysregulated immune response, and that corticosteroids improve survival of the native liver in ALF patients with high serum alanine aminotransferase levels, which are an indication of liver inflammation. However, it is unclear whether steroids are effective for pediatric acute liver failure (PALF). The aim of this retrospective case-control study is to examine whether steroid therapy for PALF accompanied by immune activation improves the survival of native liver and to identify factors that predict responses to steroid treatment.

METHODS

Of 38 patients with PALF treated at Kyoto University Hospital from February 2006 to August 2022, 19 receiving steroids who met the specific criteria for identifying the pathophysiology of immune activity in the liver (the "Steroid group"), and seven steroid-free patients who also met the criteria ("Nonsteroid group") were enrolled. Patients in the "Steroid group" were categorized as "responders" or "nonresponders" according to treatment outcome. Clinical and histological data were analyzed.

RESULTS

Survival of the native liver in the Steroid group was significantly higher than that in the Nonsteroid group (68% vs. 0%, respectively; p = 0.0052). Nonresponders were significantly younger, with higher Model for End-stage Liver Disease and pediatric end-stage liver disease scores, higher prothrombin time - international normalized ratio, and higher serum ferritin levels than responders. Massive hepatic necrosis was more common in nonresponders.

CONCLUSION

Steroid therapy is effective for PALF patients with liver inflammation; however, liver transplantation should be prioritized for young children with ALF accompanied by severe coagulopathy or massive hepatic necrosis.

Identification of pediatric activated T-cell hepatitis using clinical immune studies

BACKGROUND AND AIMS

The majority of indeterminate pediatric acute liver failure (PALF) cases are secondary to immune dysregulation, labeled activated T-cell hepatitis (TCHep). We aimed to describe a cohort of children with acute severe hepatitis and PALF and define how clinical immune labs may help identify the TCHep group.

METHODS

Retrospective review of children with acute hepatitis and PALF between March 2020 and August 2022. Patients were classified as known diagnosis, indeterminate hepatitis (IND-Hep), or TCHep (defined by liver biopsy with predominant CD8 T-cell inflammation or development of aplastic anemia).

RESULTS

124 patients were identified: 83 with known diagnoses, 16 with TCHep, and 25 with IND-Hep. Patients with TCHep had significantly increased median total bilirubin levels (7.5 mg/dL (IQR 6.8-8.9) vs 1.5 mg/dL (IQR 1.0-3.6), p < 0.0001), soluble interleukin-2 receptor levels (4512 IU/mL (IQR 4073-5771) vs 2997 IU/mL (IQR 1957-3237), p = 0.02), and percent of CD8+ T-cells expressing perforin (14.5 % (IQR 8.0-20.0) vs 1.0 % (IQR 0.8-1.0), p = 0.004) and granzyme (37.5 % (IQR 15.8-54.8) vs 4.0 % (IQR 2.5-5.5), p = 0.004) compared to IND-Hep patients. Clinical flow cytometry showed that TCHep patients had significantly increased percent CD8+ T cells (29.0 % (IQR 24.5-33.5) vs 23.6 % (IQR 19.8-25.8), p = 0.04) and HLA-DR+ (16.0 % (IQR 14.5-24.5) vs 2.7 (1.8-5.3), p < 0.001) compared to IND-Hep patients indicative of increase in CD8+ T cells that are activated.

CONCLUSIONS

Peripheral blood clinical immune studies demonstrate increased markers of CD8 T-cell activation, proliferation, and cytotoxic function for TCHep patients. These readily available immune function labs can be used to help distinguish patients with TCHep from those with other causes. This provides a non-invasive tool for early detection of potential TCHep before progression to liver failure.

Immunosuppression in two cases of indeterminate hepatitis

Background

Pediatric acute liver failure (PALF) is a potentially lethal and rapidly progressive clinical syndrome, with a large proportion of cases remaining indeterminate despite extensive investigations.

Patients and Results

In this case report, we describe two male children with indeterminate PALF and a family history of autoimmune disease, both of whom were lymphopenic with necrosis, inflammation, and lymphocytic infiltrates on their liver biopsies. One of these patients subsequently developed hepatitis-associated aplastic anemia. Notably, in addition to receiving standard liver failure care, both patients were successfully treated off-label with anti-thymocyte globulin (ATG), as well as a more prolonged course of cyclosporine and corticosteroids.

Conclusions

The fact that these medications all suppress T lymphocytes further supports the theory that T-cell activation plays a prominent role in the pathophysiology of indeterminate hepatitis. Further research should examine the short-term and long-term effects of ATG in this population, as well as the necessary duration of treatment with immune-suppressing agents.

Recent Increase in Incidence of Severe Acute Hepatitis of Unknown Etiology in Children is Associated with Infection with Adenovirus and Other Nonhepatotropic Viruses

OBJECTIVE

To evaluate whether the nature and severity of non-A-E severe acute hepatitis in children noted by the World Health Organization from late 2021 through early 2022 was indeed increased in 2021-2022 compared with prior years.

STUDY DESIGN

We performed a single-center, retrospective study to track the etiology and outcomes of children with non-A-E severe acute hepatitis in 2021-2022 compared with the prior 3-year periods (2018-2019, 2019-2020, and 2020-2021). We queried electronic medical records of children ≤16 years of age with alanine or aspartate aminotransferase levels of >500 IU. Data were analyzed for the periods of October 1, 2021, to May 1, 2022, and compared with the same time periods in 2018-2021.

RESULTS

Of 107 children meeting entry criteria, 82 cases occurred from October to May of 2018-2022. The average annual case number was 16.3 in 2018-2021 compared with a 2-fold increase (to 33) in 2021-2022 (P = .0054). Analyses of etiologies showed that this increase was associated with a higher number of children who tested positive for viruses (n = 16) when compared with the average of 3.7 for 2018-2021 (P = .018). Adenovirus (26.1%) and severe acute respiratory syndrome coronavirus-2 (10.3%) were the most frequently detected viruses in 2021-2022. Despite evidence of acute liver failure in 37.8% of children in the entire cohort and in 47% of those with viral infection, the overall survival rate was high at 91.4% and 88.9%, respectively.

CONCLUSIONS

The number of children with severe acute hepatitis in our center increased from 2021 to May 2022, with a greater frequency of cases associated with adenovirus, yet transplant-free survival remains high.

Orchestrated regulation of immune inflammation with cell therapy in pediatric acute liver injury

Acute liver injury (ALI) in children, which commonly leads to acute liver failure (ALF) with the need for liver transplantation, is a devastating life-threatening condition. As the orchestrated regulation of immune hemostasis in the liver is essential for resolving excess inflammation and promoting liver repair in a timely manner, in this study we focused on the immune inflammation and regulation with the functional involvement of both innate and adaptive immune cells in acute liver injury progression. In the context of the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) pandemic, it was also important to incorporate insights from the immunological perspective for the hepatic involvement with SARS-CoV-2 infection, as well as the acute severe hepatitis of unknown origin in children since it was first reported in March 2022. Furthermore, molecular crosstalk between immune cells concerning the roles of damage-associated molecular patterns (DAMPs) in triggering immune responses through different signaling pathways plays an essential role in the process of liver injury. In addition, we also focused on DAMPs such as high mobility group box 1 (HMGB1) and cold-inducible RNA-binding protein (CIRP), as well as on macrophage mitochondrial DNA-cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) signaling pathway in liver injury. Our review also highlighted novel therapeutic approaches targeting molecular and cellular crosstalk and cell-based therapy, providing a future outlook for the treatment of acute liver injury.

Effector memory CD8 T-cells as a novel peripheral blood biomarker for activated T-cell pediatric acute liver failure

A distinct phenotype of pediatric acute liver failure (PALF) has been identified, labeled activated T-cell hepatitis. These patients, previously included within the indeterminate group, have evidence of systemic immune activation and liver biopsy specimens with dense infiltration of CD8+ T-cells. We aimed to evaluate the peripheral blood T-cell phenotype in PALF patients with activated T-cell hepatitis compared to indeterminate cause. PALF patients with unknown etiology age 1-17 years were prospectively enrolled between 2017-2020. Within the unknown group, patients were classified as either activated T-cell hepatitis if they had a liver biopsy with dense or moderate CD8 staining and an elevated soluble interleukin-2 receptor level, or they were classified as indeterminate if they did not meet these criteria. Whole blood was collected for flow cytometry and T-cell phenotyping. Four patients with activated T-cell hepatitis and 4 patients with indeterminate PALF were enrolled. Activated T-cell hepatitis patients had significantly greater percentage of CD8 T-cells that were effector memory (TEM) phenotype compared to indeterminate PALF patients (median 66.8% (IQR 57.4-68.7) vs 19.1% (IQR 13.4-25.2), P = 0.03). In addition, CD8+ TEM cells in activated T-cell hepatitis patients were significantly more likely to be CD103 positive, a marker of tissue resident memory T-cells, compared to indeterminate PALF patients (median 12.4% (IQR 9.5-14.7) vs 4.7% (IQR 4.5-5.3), P = 0.03). We found patients with activated T-cell hepatitis can be identified by the unique pattern of increased percentage of peripheral blood effector memory CD8+ CD103+ T-cells. These findings will guide future studies exploring the T-cell phenotype for these patients and whether they may respond to directed immunosuppressive therapies.

Common mechanisms in pediatric acute liver failure

Acute liver failure (ALF) is a rare but potentially fatal disease in children. The etiology is multifactorial, including infection, autoimmune, and genetic disorders, as well as indeterminate hepatitis, which has a higher requirement for liver transplantation. Activation of the innate and adaptive immune systems leads to hepatocyte-specific injury which is mitigated by T regulatory cell activation. Recovery of the native liver depends on activation of apoptotic and regenerative pathways, including the integrated stress response (ISR; e.g., PERK), p53, and HNF4α. Loss-of-function mutations in these pathways cause recurrent ALF in response to non-hepatotropic viruses. Deeper understanding of these mechanisms will lead to improved diagnosis, management, and outcomes for pediatric ALF.

Immunological characteristics of severe acute hepatitis of unknown origin in a child post SARS-CoV-2 infection

Recent studies have reported that pediatric acute liver failure of unknown origin is immune-mediated, with CD8+ T cells playing a key role. Moreover, investigation of superantigen-mediated T-cell activation by the SARS-CoV-2 spike protein in pediatric severe acute hepatitis is needed in the context of the proposed mechanism of multisystem inflammatory syndrome in children (MIS-C). We investigated the immunological characteristics of a Japanese pediatric patient with severe acute hepatitis post SARS-CoV-2 infection. The patient demonstrated autoimmune hepatitis-like liver histology with CD8+ lymphocyte-predominant infiltration. There was Th1-type immune skewing, including remarkable peripheral CD8+ T-cell activation and a skewed T cell receptor repertoire. We also found elevated plasma levels of the anti-SARS-CoV-2 spike-specific IgG antibody, and the titer peaked after treatment, as seen with MIS-C. These findings support that immunological activation involving SARS-CoV-2 spike protein plays a crucial role in a pediatric patient with acute severe hepatitis post SARS-CoV-2 infection.

Acute severe hepatitis outbreak in children: A perfect storm. What do we know, and what questions remain?

During the first half of 2022, the World Health Organization reported an outbreak of acute severe hepatitis of unknown aetiology (AS-Hep-UA) in children, following initial alerts from the United Kingdom (UK) where a cluster of cases was first observed in previously well children aged <6 years. Sporadic cases were then reported across Europe and worldwide, although in most countries incidence did not increase above the expected baseline. There were no consistent epidemiological links between cases, and microbiological investigations ruled out known infectious causes of hepatitis. In this review, we explore the evidence for the role of viral infection, superimposed on a specific host genetic background, as a trigger for liver pathology. This hypothesis is based on a high prevalence of Human Adenovirus (HAdV) 41F in affected children, together with metagenomic evidence of adeno-associated virus (Adeno-associated viruses)-2, which is a putative trigger for an immune-mediated liver injury. Roles for superantigen-mediated pathology have also been explored, with a focus on the potential contribution of SARS-CoV-2 infection. Affected children also had a high frequency of the MHC allele HLA-DRB1*04:01, supporting an immunological predisposition, and may have been vulnerable to viral coinfections due to disruption in normal patterns of exposure and immunity as a result of population lockdowns during the COVID-19 pandemic. We discuss areas of ongoing uncertainty, and highlight the need for ongoing scrutiny to inform clinical and public health interventions for this outbreak and for others that may evolve in future.

Pediatric acute liver failure: Reexamining key clinical features, current management, and research prospects

This review aims to synthesize the most updated research, outcomes, and trends in the field of pediatric liver transplantation (LT), specifically focusing on children who have suffered from acute liver failure. Pediatric acute liver failure is a dynamic, life-threatening condition that can either self-resolve or lead to death. LT is a lifesaving intervention. With the introduction of technical variant grafts and recent immunosuppression modifications, overall patient survival, graft survival, and waitlist mortality have improved. Furthermore, recent advances in the knowledge of immunologic mediators of acute liver failure offer the possibility of more detailed understanding of the pathophysiology and new areas for research. Given the success of living donor LT for pediatric patients with acute liver failure, this option should continue to be actively considered as an alternative treatment option for patients who are listed for transplantation and are managed at a multidisciplinary tertiary care transplant center.

Characterization of a Hepatitis Outbreak in Children, 2021 to 2022

Importance

After a cluster of pediatric cases of hepatitis of unknown etiology were identified in Scotland in March 2022, the World Health Organization published an outbreak alert, and more than 1010 probable cases were reported. Some cases progressed to acute liver failure and required liver transplant. Although many patients had positive results for adenovirus on polymerase chain reaction testing from whole blood samples and/or reported recent COVID-19 infection (with or without seropositivity), the precise pathogenesis remains unclear despite the high potential morbidity of this condition.

Objective

To summarize the currently available evidence regarding novel pediatric hepatitis of unknown etiology (or novel hepatitis), encompassing case numbers, testing, management, and outcomes.

Evidence Review

A rapid review of the literature from April 1, 2021, to August 30, 2022, aimed to identify all available published case series and case-control studies of novel hepatitis. The search included PubMed and references and citations of short-listed studies.

Findings

A total of 22 available case series and case-control studies describing 1643 cases were identified, with 120 children (7.3%) receiving liver transplants and 24 deaths (1.5%). Outcome reporting and testing for adenovirus and SARS-CoV-2 was incomplete. Assessment of disease severity and management was mixed and results regarding testing for adenovirus and SARS-CoV-2 were inconsistent for both serological testing and testing of explant or biopsy liver samples. More recent studies suggest a more plausible role for adenovirus and/or adeno-associated virus 2.

Conclusions and Relevance

This systematic review without meta-analysis describes the challenge posed by hepatitis of unknown etiology in terms of investigation and management, with many cases progressing to acute liver failure. The lack of clarity regarding pathogenesis means that these children may be missing the potential for targeted therapies to improve outcomes and avert the need for transplant. Clinicians, immunologists, and epidemiologists must collaborate to investigate the pathogenesis of this novel hepatitis.

Tissue-resident memory T cells in chronic liver diseases: Phenotype, development and function

Tissue-resident memory (T_RM) T cells are a unique subset of memory T cells that are critical for the first line of defense against pathogens or antigens in peripheral non-lymphoid tissues such as liver, gut, and skin. Generally, T_RM cells are well adapted to the local environment in a tissue-specific manner and typically do not circulate but persist in tissues, distinguishing them from other memory T cell lineages. There is strong evidence that liver T_RM cells provide a robust adaptive immune response to potential threats. Indeed, the potent effector function of hepatic T_RM cells makes it essential for chronic liver diseases, including viral and parasite infection, autoimmune liver diseases (AILD), nonalcoholic fatty liver disease (NAFLD), hepatocellular carcinoma (HCC) and liver transplantation. Manipulation of hepatic T_RM cells might provide novel promising strategies for precision immunotherapy of chronic liver diseases. Here, we provide insights into the phenotype of hepatic T_RM cells through surface markers, transcriptional profiles and effector functions, discuss the development of hepatic T_RM cells in terms of cellular origin and factors affecting their development, analyze the role of hepatic T_RM cells in chronic liver diseases, as well as share our perspectives on the current status of hepatic T_RM cell research.

An Update on Pediatric Acute Liver Failure: Emerging Understanding of the Impact of Immune Dysregulation and Novel Opportunities for Intervention

Pediatric acute liver failure (PALF) is a complex, unpredictable, often rapidly progressive, potentially devastating clinical syndrome that occurs in infants, children, and adolescents without pre-existing liver disease. PALF is characterized by acute onset of hepatocellular injury and liver-based coagulopathy, frequently accompanied by hepatic encephalopathy. Etiologies include drug and toxin exposures, metabolic and genetic disorders, infections, and immune-mediated disease. PALF management primarily involves early contact with and consideration of transfer to a pediatric liver transplant center and intensive supportive multidisciplinary clinical care, with targeted therapies available for a subset of causes. Outcomes include survival with native liver, death, and liver transplantation. Efforts to develop reliable clinical prognostic tools to predict PALF outcomes early in the course of disease have not yet been fulfilled, and the possibility remains that some transplanted PALF patients might have survived without transplantation.

Pediatric Acute Liver Failure: A Clinicopathological Perspective

Pediatric acute liver failure (PALF) is a life-threatening disorder characterized by acute hepatocellular injury occurring in children without recognized underlying liver disease. The clinicopathologic evaluation of PALF requires a different approach from that in adults. The diagnostic considerations differ depending on the age, personal and family history, geographical region, and clinical presentation. Distinct entities such as gestational alloimmune liver disease, herpes simplex virus infection, and metabolic disorders should be considered in neonates with acute liver failure, while acetaminophen toxicity and autoimmune hepatitis are more frequently seen in older children and adolescents. An identified cause for PALF despite a negative complete evaluation (indeterminate) is lacking in 30 to 50% of cases. Although not routinely performed in the setting of PALF, liver biopsy may be helpful in assessing the etiology, potential mechanisms of injury, determining the appropriateness of liver transplantation, and prognostication of the patients. In this article, we review the clinicopathologic characteristics of PALF with an emphasis on general approach of pathologic evaluation and histopathologic characteristic of selected entities.

Familial hemophagocytic lymphohistiocytosis hepatitis is mediated by IFN-γ in a predominantly hepatic-intrinsic manner

Interferon gamma (IFN-γ) is the main cytokine driving organ dysfunction in Familial Hemophagocytic Lymphohistiocytosis (FHL). Blockade of IFN-γ pathway ameliorates FHL hepatitis, both in animal models and in humans with FHL. Hepatocytes are known to express IFN-γ receptor (IFN-γ-R). However, whether IFN-γ induced hepatitis in FHL is a lymphocyte or liver intrinsic response to the cytokine has yet to be elucidated. Using a IFNgR-/- bone marrow chimeric model, this study showed that non-hematopoietic IFN-γ response is critical for development of FHL hepatitis in LCMV-infected Prf1-/- mice. Lack of hepatic IFN-γ responsiveness results in reduced hepatitis as measured by hepatomegaly, alanine aminotransferase (ALT) levels and abrogated histologic endothelial inflammation. In addition, IFN-γ non-hematopoietic response was critical in activation of lymphocytes by soluble interleukin 2 receptor (sIL-2r) and recruitment of CD8+ effector T lymphocytes (CD8+ CD44hi CD62Llo) (Teff) and inflammatory monocytes. Lastly, non-hematopoietic IFN-γ response results in increased hepatic transcription of type 1 immune response and oxidative stress response pathways, while decreasing transcription of genes involved in extracellular matrix (ECM) production. In summary, these findings demonstrate that there is a hepatic transcriptional response to IFN-γ, likely critical in the pathogenesis of FHL hepatitis and hepatic specific responses could be a therapeutic target in this disorder.

Emergencies in paediatric hepatology

The aetiology of several liver diseases in children is age specific and many of these conditions have significant and potentially long-term clinical repercussions if not diagnosed early and managed in a timely fashion. We address 5 clinical scenarios that cover most of the diagnostic and therapeutic emergencies in children: infants with liver disease; acute liver failure; management of bleeding varices; liver-based metabolic disorders; and liver tumours and trauma. A wide spectrum of conditions that cause liver disease in infants may present as conjugated jaundice, which could be the only symptom of time-sensitive disorders - such as biliary atresia, metabolic disorders, infections, and haematological/alloimmune disorders - wherein algorithmic multistage testing is required for accurate diagnosis. In infantile cholestasis, algorithmic multistage tests are necessary for an accurate early diagnosis, while vitamin K, specific milk formulae and disease-specific medications are essential to avoid mortality and long-term morbidity. Management of paediatric acute liver failure requires co-ordination with a liver transplant centre, safe transport and detailed age-specific aetiological work-up - clinical stabilisation with appropriate supportive care is central to survival if transplantation is indicated. Gastrointestinal bleeding may present as the initial manifestation or during follow-up in patients with portal vein thrombosis or chronic liver disease and can be managed pharmacologically, or with endoscopic/radiological interventions. Liver-based inborn errors of metabolism may present as encephalopathy that needs to be recognised and treated early to avoid further neurological sequelae and death. Liver tumours and liver trauma are both rare occurrences in children and are best managed by a multidisciplinary team in a specialist centre.

Proceedings of the European Society for Pediatric Gastroenterology, Hepatology and Nutrition Monothematic Conference, 2020: "Acute Liver Failure in Children": Treatment and Directions for Future Research

OBJECTIVES

The Hepatology Committee of the European Society for Pediatric Gastroenterology, Hepatology and Nutrition (ESPGHAN) aims to educate pediatric gastroenterologists, members of ESPGHAN and professionals from other specialties promoting an exchange of clinical expertise in the field of pediatric hepatology.

METHODS

The 2020 single topic ESPGHAN monothematic 3-day conference on pediatric liver disease, was organized in Athens, Greece and was entitled " Acute Liver Failure" (ALF). ALF is a devastating disease with high mortality and in a considerable fraction of patients, the cause remains unresolved. As knowledge in diagnosis and treatment of ALF in infants and children has increased in the past decades, the objective was to update physicians in the field with developments in medical therapy and indications for liver transplantation (LT) and to identify areas for future research in clinical and neurocognitive outcomes in ALF.

RESULTS

We recently reported the epidemiology, diagnosis, and initial intensive care management issues in separate manuscript. Herewith we report on the medical treatment, clinical lessons arising from pediatric studies, nutritional and renal replacement therapy (RRT), indications and contraindications for LT, neurocognitive outcomes, new techniques used as bridging to LT, and areas for future research. Oral presentations by experts in various fields are summarized highlighting key learning points.

CONCLUSIONS

The current report summarizes the current insights in medical treatment of pediatric ALF and the directions for future research.

North American Society for Pediatric Gastroenterology, Hepatology, and Nutrition Position Paper on the Diagnosis and Management of Pediatric Acute Liver Failure

ABSTRACT

Pediatric acute liver failure (PALF) is a rare, rapidly progressive clinical syndrome with significant morbidity and mortality. The phenotype of PALF manifests as abrupt onset liver dysfunction, which can be brought via disparate etiology. Management is reliant upon intensive clinical care and support, often provided by the collaborative efforts of hepatologists, critical care specialists, and liver transplant surgeons. The construction of an age-based diagnostic approach, the identification of a potential underlying cause, and the prompt implementation of appropriate therapy can be lifesaving; however, the dynamic and rapidly progressive nature of PALF also demands that diagnostic inquiries be paired with monitoring strategies for the recognition and treatment of common complications of PALF. Although liver transplantation can provide a potential life-saving therapeutic option, the ability to confidently determine the certainness that liver transplant is needed for an individual child has been hampered by a lack of adequately tested clinical decision support tools and accurate predictive models. Given the accelerated progress in understanding PALF, we will provide clinical guidance to pediatric gastroenterologists and other pediatric providers caring for children with PALF by presenting the most recent advances in diagnosis, management, pathophysiology, and associated outcomes.

Sudden onset hepatitis in children

The recent increase in unexplained acute hepatitis in children in 2022 has focused attention on acute paediatric liver disease. We discuss emerging evidence and leading causal hypotheses in context with potential long-term effects of the COVID-19 pandemic for young children.

Transcriptional Analysis of Liver Tissue Identifies Distinct Phenotypes of Indeterminate Pediatric Acute Liver Failure

Many patients with indeterminate pediatric acute liver failure (PALF) have evidence of T-cell driven immune injury; however, the precise inflammatory pathways are not well defined. We have characterized the hepatic cytokine and transcriptional signatures of patients with PALF. A retrospective review was performed on 22 children presenting with indeterminate (IND-PALF; n = 17) or other known diagnoses (DX-PALF; n = 6) with available archived liver tissue. Specimens were stained for clusters of differentiation 8 (CD8) T cells and scored as dense, moderate, or minimal. Measurement of immune analytes and RNA sequencing (RNA-seq) was performed on whole-liver tissue. Immune analyte data were analyzed by principal component analysis, and RNA-seq was analyzed by unsupervised hierarchical clustering, differential gene expression, and gene-set enrichment analysis. Most patients with IND-PALF (94%) had dense/moderate CD8 staining and were characterized by Th1 immune analytes including tumor necrosis factor α, interferon γ (IFN-γ), interleukin (IL) 1β, IL-12, C-X-C motif chemokine ligand (CXCL) 9, and CXCL12. Transcriptional analyses identified two transcriptional PALF phenotypes. Most patients in group 1 (91%) had IND-PALF and dense/moderate CD8 staining. This group was characterized by increased expression of genes and cell subset-specific signatures related to innate inflammation, T-cell activation, and antigen stimulation. Group 1 expressed significantly higher levels of gene signatures for regulatory T cells, macrophages, Th1 cells, T effector memory cells, cytotoxic T cells, and activated dendritic cells (adjusted P < 0.05). In contrast, patients in group 2 exhibited increased expression for genes involved in metabolic processes. Conclusion: Patients with IND-PALF have evidence of a Th1-mediated inflammatory response driven by IFN-γ. Transcriptional analyses suggest that a complex immune network may regulate an immune-driven PALF phenotype with less evidence of metabolic processes. These findings provide insight into mechanisms of hepatic injury in PALF, areas for future research, and potential therapeutic targets.