Extranodal rosai-dorfman disease presenting as a solitary mass with human herpesvirus 6 detection in a pediatric patient.

In Rosai-Dorfman disease (RDD), exclusive extranodal involvement with lesions limited to the kidneys is very uncommon and has been described only in adult patients. Occasionally, human herpesvirus 6 (HHV-6) has also been detected in RDD tissue samples. We present the case of a 7-year-old boy referred to our center presenting a single solid mass in the right kidney measuring 3.4 cm, detected both on contrast computed tomography and magnetic resonance imaging. Surgical excision was successfully completed, and the pathology report informed characteristic histopathology and immmunohistochemistry features of RDD. Human herpesvirus 6 was detected and amplified by polymerase chain reaction, as well as by immunohistochemistry. We discuss imaging and histology-based differential diagnoses in the pediatric age group. Although RDD is a rare histiocytic disorder of unknown etiology and pathogenesis, the presence of HHV-6 observed in this case supports the possibility of an abnormal immunologic response linked to viral presence.

HHV-6-related acute liver failure in two immunocompetent adults: favourable outcome after liver transplantation and/or ganciclovir therapy.

Fulminant hepatitis of unknown origin remain a significant cause of mortality, for which liver transplantation is often considered as the only therapeutic option. In retrospective studies, human herpesvirus 6 (HHV-6) infections have been associated with such diseases, but the diagnosis of HHV-6 infection of the liver is rarely established during the acute phase of liver failure. Using real-time polymerase chain reaction (PCR), we diagnosed two cases of severe acute liver failure (ALF) related to HHV-6 occurring in immunocompetent young adults. Both cases had a favourable outcome, one after valganciclovir therapy, one after liver transplantation associated with ganciclovir. Viral origin was evidenced in each case by the detection of high amounts of HHV-6 DNA in liver tissue by the PCR assay. The decrease of intrahepatic viral load after therapeutic intervention was also monitored by quantitative PCR and paralleled in the two cases the clinical improvement. Diagnosis of HHV-6 infection must be systematically evoked in case of unexplained ALF, since it might lead to specific therapeutic interventions, in addition of liver transplantation.