Prolonged sinus tachycardia caused by human herpesvirus 6 (HHV6) encephalomyelitis after allogeneic bone marrow transplantation.

A 19-year-old man with Philadelphia chromosome-positive acute lymphoblastic leukemia received an allogeneic hematopoietic cell transplant with unrelated bone marrow. On day 20, the patient developed impaired consciousness and disorientation. Examination of the cerebrospinal fluid showed 2×10(4) copies/mL of HHV6B. HHV6 encephalitis was diagnosed, as had HHV6 myelitis based on symptoms that included lancinating pain/pruritus in the lower limbs and dysuria/dyschezia. Concurrently, he showed sinus tachycardia. Even after clearance of the HHV6 genome from the plasma and CSF was achieved by treatment with foscarnet, sinus tachycardia persisted for another 100 days. We suspected prolonged sinus tachycardia due to dysautonomia caused by HHV6 encephalomyelitis.