Case report: Acute liver failure in children and the human herpes virus 6-? A factor in the recent epidemic

The Outbreak of Unexplained Acute Hepatitis in Children: The Role of Viral Infections in View of the COVID-19 Pandemic

BACKGROUND AND AIMS

An increase in the number of cases of acute hepatitis of unknown origin (HUO) in children was observed in 2021. Adenovirus and adeno-associated virus 2 (AAV2) infections have been suggested as possible triggers. However, the potential etiology is still unclear. We aimed to characterize a cohort of children with HUO in Israel in view of the COVID-19 pandemic.

METHOD

Demographics, clinical data, and laboratory results on the children compatible with the CDC criteria for HUO were collected by the established registry of the Ministry of Health. Available specimens were sent to the Central Virology Laboratory.

RESULTS

A total of 39 children were included in the registry. A total of 20 were enrolled prospectively, in which human herpes virus 6 (HHV6) infection or reactivation was identified in 11/19, adenovirus was found in 4/19 of the cases, and AAV2 was detected in 2/16. Past COVID-19 exposure was recorded for 24/39 of the children. A total of 10 children underwent liver biopsy, and 8 were successfully treated with steroids and 2 underwent liver transplantation.

CONCLUSIONS

The COVID-19 pandemic and the related containment measures combined with reactivation or active infection with other viruses could have been a trigger for the HUO outbreak. In our cohort, HHV6 was the most abundant finding.

Could Herpesviridae be the cause of severe acute hepatitis of unknown origin in children?

INTRODUCTION

Severe acute hepatitis (SAH) is defined by a severe inflammation of hepatocytes in the liver parenchyma which can lead to an acute liver failure, a clinical condition with high mortality rate that can be triggered by several factors but is usually associated to hepatotropic viruses' infection. In 2022, cases of children with severe acute hepatitis of unknown origin hospitalized in Glasgow, Scotland, were reported. Possible causes of this condition include, but are not limited to, undiagnosed viral (and non-viral) infections, autoimmune hepatitis, drug and/or chemical toxicity, mitochondrial chain respiratory and metabolic disorders.

AREAS COVERED

Herpesviruses can cause severe acute hepatitis, but little is known about the role and the mechanisms of herpesviruses as a causative agent of this type of hepatitis. We review the role of herpesviruses as causative agent of SAH in children and other possible mechanisms involved in this disease.

EXPERT OPINION

Differential diagnosis for herpesvirus in SAH should be implemented in all settings. Alternative fluids, such as saliva and dried blood, could be used in the diagnosis to overwhelm the availability of biological specimens at sufficient volume. In the future, genetic studies could also be added to increase the knowledge about severe acute hepatitis in children.

Non-A to E hepatitis in children: Detecting a novel viral epidemic during the COVID-19 pandemic

During the COVID-19 pandemic, two further novel viral epidemics were described in 2022, monkeypox virus infections in men having sex with men and non-A to E hepatitis in children. The latter occurred in the first half of 2022 with about 1000 cases worldwide, necessitating liver transplantation in 5% and causing death in 2% of patients. It took some effort to clarify the cause of the novel hepatitis epidemic. Researchers were confronted with a polymicrobial viral infection consisting of an adenovirus-associated virus type 2 (AAV2) infection, co-occurring with either human adenovirus type 41 (HAdV41) or herpesvirus infections; most prominently human herpesvirus type 6 (HHV-6). AAV-2, a small Dependovirus of the Parvovirus family, needs these helper viruses for its replication. AAV2 is used as a vector for liver-targeting gene therapy but was not previously known to cause acute hepatitis. HAdV41 and HHV-6 are mostly known to cause diarrhoea and febrile illnesses associated with skin rashes in children, respectively. Except for a few case reports of HHV-6 hepatitis, HAdV and HHV-6 are mostly known as major pathogens in immunosuppressed transplantation patients. A potential role of SARS-CoV-2 has also been discussed but the most popular hypothesis involves an indirect role of the COVID-19 pandemic for this novel disease. Exposure to HHV-6 infections occurs nearly quantitatively during the first year of life. Social distancing measures, followed by the lifting of these measures in 2022 might have caused a delayed exposure to multiple, normally benign childhood viral infections eliciting a dysregulated immune response with pathological effects for liver cells. In the fall of 2022, when these conditions were not longer met, case numbers dwindled. The hypothesis of an unequilibrated immune response instead of intrinsic cytopathic activity of the implicated viruses is further supported by the enrichment of a particular HLA allele in cases over controls.