To describe an atypical presentation of progressive multifocal leukoencephalopathy (PML) in a young female with idiopathic CD4 lymphocytopenia.   

A 45-year old female presented with an acute onset of right homonymous hemianopia. She had a history of difficulty in thought process and memory issues which was subacute in onset. Brain magnetic resonance imaging (MRI) revealed restricted diffusion in left occipital region. Contrast vessel studies of head and neck evidenced mild beading pattern. Initial diagnosis of concern for her symptoms was primary cerebral vasculitis , treated with oral prednisolone. Patient deteriorated clinically and radiologically on corticosteroids therapy. Repeat MRI of brain revealed an extensive non-enhancing signal abnormality of the left occipital region which extended into the right parietal-occipital region through corpus callosum. Brain biopsy and cerebrospinal fluid polymerase chain reaction was positive for JCV, suggestive of PML. Extensive work up for immunosuppression was negative except for evidence of low CD4 count to 6. This patient was finally diagnosed to have PML in the setting of ICDL who died after two months due to its poor prognosis.

PML can occur in patients without any recognizable immunodeficiency. ICDL as the cause for PML is rare. Radiologically, it can mimic an acute ischemic stroke. Knowledge of this association is important for institution of appropriate therapy.