Parvovirus B19-Associated Meningoencephalitis in an Adult: A Rare Cause of Central Nervous System Infection

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Parvovirus B19 (B19V) is a common childhood pathogen but a rare cause of central nervous system (CNS) disease in adults.Neurological manifestations are diverse, cerebrospinal fluid (CSF) findings are often nonspecific, and interpreting a positive molecular result in CSF can be difficult.A previously healthy 42-year-old woman presented with progressive headache, photophobia, and diplopia, and later developed generalized tonic-clonic seizures and encephalopathy.On hospital day 5, she deteriorated with reduced consciousness, requiring intubation and intensive care.Serial MRI showed progressive gyriform fluid-attenuated inversion recovery (FLAIR) hyperintensity, new bilateral thalamic, basal ganglia, and basal cistern signal change, and diffuse meningeal enhancement.CSF was acellular with elevated protein (117 mg/dL) and glucose of 30 mg/dL (1.7 mmol/L); with a paired serum glucose of 5.5 mmol/L, the CSF-to-serum glucose ratio was 0.30.A multiplex real-time viral PCR panel detected B19V DNA in CSF, with all 10 other viral targets, including herpes simplex virus types 1 and 2 (HSV-1/2), varicellazoster virus (VZV), and enterovirus, not detected.B19V immunoglobulin M (IgM) and immunoglobulin G (IgG), tested about two weeks later, were negative.She received empirical antimicrobials, high-dose corticosteroids, a five-day course of intravenous immunoglobulin (IVIG), and supportive care, and was extubated on hospital day 16.At follow-up, she had fatigue, photophobia, a postural tremor that later improved, globally reduced reflexes, and a residual left sixth cranial nerve palsy.This case is consistent with B19V-associated meningoencephalitis, but the discordance between CSF PCR positivity and negative serology limits diagnostic certainty.The residual deficits may reflect postencephalitic sequelae, raised intracranial pressure, or nerve involvement, and could not be distinguished further.Recovery followed multimodal treatment, so the contribution of any single therapy cannot be determined.B19V may be considered in adults with unexplained meningoencephalitis when routine investigations are negative.A positive CSF PCR should be interpreted alongside serology, blood PCR where available, and a thorough exclusion of alternative causes.Thus, early recognition facilitated by molecular diagnostics, combined with supportive and immunomodulatory therapy, may improve outcomes and reduce long-term neurological sequelae.