Successful ganciclovir therapy in a patient with human herpesvirus-6 encephalitis after unrelated cord blood transplantation: usefulness of longitudinal measurements of viral load in cerebrospinal fluid

Background There have been no reports of human herpesvirus-6 (HHV-6) encephalitis treatment based on both HHV-6 DNA load and the antiviral agent’s concentration in the cerebrospinal fluid (CSF). Patient A 20-year-old male with a hematological malignancy developed HHV-6 encephalitis 15 days after unrelated cord blood transplantation (UCBT). He had fever, chest pain, memory impairment, and insomnia. His CSF showed no increased cell counts, but the amount of HHV-6 DNA was elevated to 2.0 × 10 6 copies/ìgDNA. Magnetic resonance imaging (MRI) of the head revealed abnormal high-intensity signals in the left limbic system on T2-weighted and diffusion-weighted images. Intravenous administration of ganciclovir (GCV) was initiated at 5 mg/kg every 12 h on day 18, and was continued until day 137. The amount of HHV-6 DNA in the plasma became undetectable on day 25. The HHV-6 load in the CSF decreased to 1.5 × 10 3 copies/ìgDNA on day 32, and reached undetectable levels on day 53. The mean concentration of GCV 1 h after an infusion of 5 mg/kg was 4.12 mg/mL in plasma and 0.7 mg/mL in CSF. The chest pain and insomnia disappeared on days 35 and 47, respectively. Memory defects recovered up to day 85. Conclusion Serial quantification of HHV-6 DNA in CSF may be useful for successful treatment with GCV in post-transplant HHV-6 encephalitis.