Herpes zoster meningitis presenting with a cerebrospinal fluid leukemoid reaction in an adolescent with preB-ALL in remission

A 19-year-old girl with a history of precursor B acute lymphoblastic leukemia in remission presented with fever, headache, and a skin rash. Cerebrospinal fluid (CSF) examination reported pleocytosis with blast-like cells concerning for a central nervous system leukemic relapse. After the patient showed significant improvement on intravenous acyclovir, a repeat lumbar puncture revealed normalization of CSF. The abnormal CSF cells were reviewed and ultimately determined to be activated and atypical lymphocytes. The patient recovered uneventfully. Atypical lymphocytes resembling leukemic blasts are an unusual finding in viral meningitis. Varicella zoster virus reactivation should be considered during initial evaluation for central nervous system relapse of leukemia.