The diagnosis of HEV infection is technically challenging and should be made simultaneously with RT-PCR methods, viral load quantification and serological markers. In immunosuppressed children who develop chronic hepatitis, the prevalence of HEV is high and could explain the chronic liver inflammation potentially leading to cirrhosis. Re-infection by different HEV strains from zoonotic transmission can result in progressive liver disease in immunocompromised children.

TTV infection is widespread, and its replication is closely related to immune status and viral coinfection. High TTV viremia is not associated with hepatitis after OLT, but, conversely, liver inflammatory activity impairs TTV replication.

PN in MVID is difficult to manage and requires expertise. Despite improved results in expert centers, the risk of death or irreversible sequelae is higher with PN than after Tx. SBTx, despite being complicated, remains the only hope to improve the quality of life and long-term prognosis of these children.