Varicella-zoster virus encephalitis in an elderly patient with influenza A infection.

Varicella-zoster virus (VZV) encephalitis is a rare but severe condition associated with significant morbidity and mortality. Its clinical presentation is often nonspecific and may overlap with other neurological conditions, including complications of influenza infection. We report a case of a 76-year-old man with confirmed influenza A infection who developed progressive neurological deterioration. Notably, no cutaneous manifestations suggestive of herpes zoster were observed. Cerebrospinal fluid analysis revealed lymphocytic pleocytosis, and polymerase chain reaction confirmed the presence of VZV DNA. The patient was treated with intravenous acyclovir, resulting in clinical improvement and full neurological recovery. This case highlights the diagnostic challenges of acute neurological manifestations during influenza infection, where symptoms may be attributed to influenza-related complications. It underscores the importance of considering VZV reactivation, particularly in elderly patients, even in the absence of typical cutaneous manifestations, to ensure timely diagnosis, appropriate antiviral treatment, and improved clinical outcomes.