A case of human herpesvirus-6 encephalitis, carditis, infantile spasms, and a subsequent cerebellar astrocytoma containing the HHV-6 genome, is reported from the University of Oulu, Finland. A 14-month-old girl presented with fever, hypotonia, and a diffuse urticarial exanthem. After admission, she developed encephalitis and status epilepticus, followed by myocarditis. MRI of the brain showed thin subdural effusions but no tumor. After 11 weeks from onset, convulsions changed to infantile spasms, resistant to vigabatrin and ACTH. A repeat MRI at 11 months after the primary illness showed a cystic astrocytoma located near the vermis. Five months after surgical removal of the tumor, the patient has hypotonia, poor social communication, and daily infantile spasms. HHV-6 DNA was detected by PCR in the tumor tissue. 
COMMENT. This is the first reported case of HHV-6 association with subsequent infantile spasms and pilocytic cerebellar astrocytoma. HHV-6 DNA found in the tumor cells may indicate a causative role for the virus or simply an invasion of the tumor by the virus. The absence of MRI evidence for a tumor at the onset of infection is in favor of the former explanation. Laboratory studies have demonstrated oncogenic properties of HHV-6 virus.