Progressive Multifocal Leukoencephalopathy: A Rare Cause of Altered Mentation.

Progressive multifocal leukoencephalopathy (PML) is a rare demyelinating neurologic disease caused by the John Cunningham virus (JCV). Most affected patients have human immunodeficiency virus (HIV), but medications are also a risk factor. It can be difficult to diagnose PML as it can present with a broad range of symptoms, especially if other conditions are present that also contribute to encephalopathy. We report a case of a patient who developed PML from medications rarely associated with PML in the setting of multiple comorbid medical conditions that contributed to diagnostic delay. A 63-year-old female patient presented with subacute, intermittent encephalopathy, weakness, and dysphagia. She had a known history of cirrhosis, Sjogren's syndrome, and sarcoidosis, for which she was on chronic azathioprine and prednisone. Initial workup showed laboratory and exam findings consistent with hepatic encephalopathy (HE) and cystitis. Despite appropriate treatment, her condition worsened, and magnetic resonance imaging found confluent white matter lesions throughout her brain. Lumbar puncture was positive for JCV DNA, and she passed away soon after diagnosis. Only one other case report of a patient developing PML while taking both azathioprine and prednisone for sarcoidosis exists. Patients with PML commonly experience cognitive disturbances, which can mimic more common disease processes, such as HE and infections. Our patient presented with these comorbid conditions, which delayed diagnosis. There are no established treatment options for PML patients without HIV except withdrawal of the offending medications. Clinicians must maintain awareness to diagnose PML as it has a broad presentation pattern, and comorbid conditions can further complicate diagnosis. Patients should be maintained on the minimally effective dose of immunosuppression to reduce the risk of PML development.