Human Herpesvirus 6 (HHV-6) Encephalitis in a Non-Transplant Patient With Polymyositis

Human herpesvirus 6 (HHV-6) was initially labeled as a human B lymphotropic virus because it was isolated in patients diagnosed with lymphoproliferative disorders. There are two variants of HHV-6: HHV-6A and HHV-6B. A considerable majority of recorded primary infections and reactivation events are primarily due to HHV-6B. We report a case of HHV-6 encephalitis reactivation in a 75-year-old Caucasian diabetic female with a past medical history of polymyositis treated with prednisone for a long time who presented with generalized weakness and drowsiness. She developed her symptoms after contact with her grandchildren, who recently had viral-like symptoms treated with antibiotics. Magnetic resonance imaging (MRI) of the brain without contrast showed 14 mm high transverse relaxation time (T2)/fluid-attenuated inversion recovery (FLAIR) signal intensity focus on the left temporal lobe, suspicious for primary versus metastatic neoplasm. Cerebrospinal fluid analysis found that protein concentration was 75 mg/dl, glucose concentration 55 mg/dl, white blood cell count was 22/mm3, with a lymphocytic predominance. Meningitis/encephalitis polymerase chain reaction (PCR) panel detected HHV-6. She was discharged after treatment with ganciclovir for 14 days. It is crucial to recognize HHV-6 infections in immunocompromised patients who present with a T2/FLAIR signal intensity focus in the left temporal lobe. In a hospital setting, rapid HHV-6 encephalitis testing is important to make a correct diagnosis to avoid any delay to prevent further morbidity and mortality.