Rashless varicella-zoster virus encephalitis diagnosed by metagenomic next-generation sequencing: two case reports.

BACKGROUND: Varicella-zoster virus (VZV) can cause a range of central nervous system (CNS) infections, but early diagnosis is difficult when typical skin rash is absent. Rashless VZV encephalitis may present with nonspecific clinical, cerebrospinal fluid (CSF), and neuroimaging findings and can mimic autoimmune encephalitis, primary central nervous system lymphoma, or other disorders. We report two cases of rashless VZV encephalitis diagnosed by CSF metagenomic next-generation sequencing (mNGS), with subsequent neurological complications.

CASE PRESENTATION: Case 1 was a 68-year-old man admitted with fever, seizures, and impaired consciousness. Brain magnetic resonance imaging (MRI) showed multifocal abnormal signals. CSF analysis revealed marked pleocytosis and elevated protein levels, and CSF cytology showed suspected atypical lymphocytes, leading to early consideration of autoimmune encephalitis and primary central nervous system lymphoma. CSF mNGS detected VZV, and rashless VZV encephalitis was diagnosed. The patient improved after intravenous acyclovir combined with a short course of dexamethasone. On day 45 after disease onset, follow-up MRI showed a new acute cerebral infarction adjacent to the posterior horn of the left lateral ventricle. Recurrent CSF pleocytosis and persistent protein elevation suggested possible VZV-associated vasculopathy. After repeated antiviral treatment, he improved again, and no recurrence was observed during more than 3 years of follow-up. Case 2 was a 74-year-old man admitted with fever, low back pain, vomiting, and impaired consciousness. Brain MRI showed multifocal abnormal signals, and CSF analysis revealed marked inflammatory changes. CSF mNGS detected VZV, supporting the etiological diagnosis of rashless VZV encephalitis. The patient improved after intravenous acyclovir combined with a short course of dexamethasone. On day 14 after disease onset, he developed urinary retention, impaired defecation sensation, and bilateral lower-limb weakness, suggesting possible lumbosacral nerve root or cauda equina involvement. Suspected VZV-related Elsberg syndrome was considered. His urinary and bowel dysfunction recovered at 2 months after disease onset.

CONCLUSIONS: Rashless VZV encephalitis may be diagnostically challenging because early clinical, CSF, and neuroimaging findings are nonspecific. CSF mNGS can support etiological diagnosis, and careful follow-up is needed to detect delayed vascular and lumbosacral nerve root complications.