Chronic Dengue Virus Encephalitis: A Case Study and Metagenomic Analysis

Dengue virus (DENV) infection can cause acute encephalitis. Chronic encephalitis with progressive dementia is rarely reported.

We present a case of chronic encephalitis with rapidly progressive dementia, in which a potential DENV brain infection was identified with brain tissue metagenomic next-generation sequencing. Brain pathology and molecular diagnosis are also presented.

A 20-year-old man from SP, Brazil, presented with rapidly progressive dementia, speech apraxia, and apathy in June 2022. By January 2023, cognitive testing showed severe global impairment (MMSE score of 18/30). MRI revealed white matter abnormalities and atrophy; CSF analysis disclosed a mild lymphocytic pleocytosis, mildly elevated protein levels, and positive CSF oligoclonal bands. Despite extensive testing ruling out common infectious and inflammatory causes, the patient's condition worsened with executive dysfunction, language impairment, tremors, and myoclonus. In August 2023, a brain biopsy and next-generation sequencing identified DENV-1 genotype V, linked to Brazilian sequences from 2000 to 2022.

This case highlights a challenging instance of encephalitis with unknown etiology, where metagenomic analysis detected DENV-1 RNA in brain tissue, suggesting a possible cause.