Progressive multifocal leukoencephalopathy in an immunocompetent patient

A 69-year old man presents with a subacute history of worsening confusion, anxiety and abnormal gait. Brain MRI revealed an extensive non-enhancing signal abnormality of parieto-occipito-temporal white matter. CSF PCR was positive for JC virus, suggestive of progressive multifocal leukoencephalopathy (PML). Extensive workup for occult immunosuppression was negative. Although PML in an immunocompetent patient is exceedingly rare, biopsy confirmed the diagnosis. Mirtazapine and mefloquine therapies were initiated and JCV DNA titre decreased by 100-fold at six months. One year later, his clinical course had stabilized and neuroimaging was improved. Our case suggests that PML can rarely afflict immunocompetent individuals and that serotonin receptor targeting pharmacological therapy may improve the outcome.