ABSTRACT
BACKGROUND: Encephalitis caused by Herpes Simplex Virus-1 is a devastating disease with high mortality and disability rates despite adequate treatment. No clear risk factors have been identified although iatrogenic immunosuppression has been suggested, among others. CASE REPORT: A 59-year-old male smoker was diagnosed with metastatic lung adenocarcinoma and was treated with brain and spinal irradiation. Ten days after the completion of radiotherapy and before initiating platinum-based front-line chemotherapy, he developed low grade fever and personality change. Over the next few days, high fever and refractory seizures developed and the patient was diagnosed with Herpes simplex-associated encephalitis after detection of viral DNA in the cerebrospinal fluid via polymerase chain reaction. Despite treatment with acyclovir, the patient remained comatose and died three months after the initial presentation. CONCLUSION: This case illustrates a possible association between brain irradiation and increased risk for Herpes simplex-associated encephalitis. However, the underlying mechanisms have not been elucidated.