A case of human herpesvirus 6 encephalitis following pediatric hematopoietic stem cell transplantation: early diagnosis and treatment matters


Human herpesvirus 6 (HHV-6) is one of the life-threatening infectious complications with significant morbidity and mortality following hematopoietic stem cell transplantation (HSCT). Clinically, the diagnosis of HHV-6 encephalitis can be challenging due to a lack of specific symptoms and definitive diagnostic tests. We report a pediatric HSCT recipient who developed late-onset HHV-6 encephalitis without typical radiographic findings. The routine viral infection monitoring protocol contributed to the prompt diagnosis of HHV-6 encephalitis and early therapeutic intervention. The patient was treated successfully without any neurological complications attributable to HHV-6 encephalitis. HHV-6 encephalitis should remain in the differential diagnosis as an important but treatable disease, even for several months after HSCT and even without radiographic findings. Whenever HHV-6 encephalitis is suspected, antivirals should be initiated promptly to prevent its complications.

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Fig. 1
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Human herpesvirus 6


Hematopoietic stem cell transplantation


Central nervous system


Cerebrospinal fluid


X-linked inhibitor of apoptosis


Bone marrow transplantation






Anti-thymocyte globulin


Graft-versus-host disease


Hemophagocytic lymphohistiocytosis




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The authors wish to thank the medical editors from the Department of Education for Clinical Research of the National Center for Child Health and Development for editing this manuscript. This study was supported in part by a grant from the National Center for Child Health and Development, grant numbers 28-5 and 30-3.

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Correspondence to Masaki Yamada.

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Sakamoto, A., Yamada, M., Tsujimoto, S. et al. A case of human herpesvirus 6 encephalitis following pediatric hematopoietic stem cell transplantation: early diagnosis and treatment matters. Int J Hematol (2020). https://doi.org/10.1007/s12185-020-02905-x

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  • Hematopoietic stem cell transplantation
  • Human herpesvirus 6
  • Post-transplant encephalitis
  • Viral load