Case

A 68-year-old woman presented with 3 weeks of progressive left-sided weakness. She had a history of Sjögren’s syndrome, complicated by mononeuritis multiplex and arteritic anterior ischaemic optic neuropathy, and had taken azathioprine for 14 months. On examination, she was disorientated, inattentive, with a left hemiparesis and extensor left plantar response. MR scan of brain showed asymmetrical bilateral frontoparietal leukoencephalopathy, involving U-shaped fibres and deep white matter, with foci of diffusion restriction in the right frontoparietal and left parietal lobes, and a thin, linear, gyriform susceptibility weighted imaging (SWI)-hypointense rim in the periphery of the lesion (figure 1). Cerebrospinal fluid (CSF) examination showed 2 white cells/µL (≤5), glucose 5.6 mmol/L (2.5–4.4) and protein 0.44 g/L (0.15–0.45); Gram stain was negative. Quantitative DNA polymerase chain reaction (PCR) in CSF for JC (John Cunningham) polyomavirus was positive, supporting the diagnosis of progressive multifocal leukoencephalopathy (PML), an infective and life-threatening demyelinating disease of …