HHV-6: an unusual cause of cerebellar ataxia.

Human herpesvirus 6 (HHV-6) infection is the cause of roseola infantum in children. The reactivation of HHV-6 is associated with multiple clinical syndromes including encephalitis and myelitis, especially in haematopoietic stem cell transplant recipients. However, the virus can cause encephalitis in other immunosuppressed as well as immunocompetent individuals. We report a case of a 70-year-old woman who was immunocompromised secondary to treatment of rheumatoid arthritis with leflunomide and methotrexate. The patient presented with acute ataxia, diplopia and dysarthria. MRI brain showed an enhancing lesion in the midbrain. The diagnosis of HHV-6 encephalitis was made after HHV-6 A DNA was detected in both serum and cerebrospinal fluid. Treatment consisted of a 3-week course of intravenous ganciclovir along with physiotherapy. At a 3-month follow-up, repeat MRI brain showed a decrease in size and oedema of the lesion and the patient's neurological function was improved.