Evidence for human herpesvirus-6B infection of regulatory T-cells in acute systemic lymphadenitis in an immunocompetent adult with the drug reaction with eosinophilia and systemic symptoms syndrome: a case report.

We describe a fatal case of drug reaction with eosinophilia and systemic symptoms (DRESS) syndrome with human herpesvirus-6B (HHV-6B)-associated lymphadenitis and virus-associated hemophagocytic syndrome triggered by an over-the-counter medication to treat respiratory and influenza-like symptoms. Histologically, the structure of the lymph node was disrupted with infiltration of large lymphocytes carrying intranuclear acidophilic inclusion bodies. Immunohistochemistry and real-time PCR analysis revealed that these large lymphocytes were positive for HHV-6B. Numerous HHV-6 particles were detected in the inclusion body of the lymphocytes by electron microscopy. Interestingly, immunohistochemistry revealed that HHV-6B-infected cells in the lymph node were CD3(+), CD4(+), CD25(+), and FoxP3(+) T cells, indicating a phenotypic resemblance to regulatory T-cells. This case provides direct evidence of HHV-6 infection in CD25(+)/FoxP3(+) T cells in a case of acute lymphadenitis of DRESS syndrome, suggesting a significant role of HHV-6 infection of regulatory T-cells in the pathogenesis of DRESS syndrome.