Asymptomatic progressive multifocal leukoencephalopathy: a case report and review of the literature

We report the development of asymptomatic progressive multifocal leukoencephalopathy in a patient with multiple sclerosis on natalizumab therapy. Progressive multifocal leukoencephalopathy often presents with debilitating neurologic symptoms. Very few cases have documented a completely asymptomatic course of the disease.

A 26-year-old white woman with multiple sclerosis was treated with natalizumab. She was diagnosed as having progressive multifocal leukoencephalopathy based on characteristic magnetic resonance imaging lesions after 27 infusions of natalizumab. She had no neurologic deficits at the time of diagnosis and John Cunningham virus in cerebrospinal fluid was detected at 15 copies/ml. She was initially treated with mefloquine and mirtazapine and remained asymptomatic for 3 months. She later developed worsening magnetic resonance imaging lesions related to immune reconstitution inflammatory syndrome. At that time, she received intravenously administered immunoglobulin and high-dose intravenously administered methylprednisolone with radiologic improvement of the lesions.

Our case report illustrates that early detection of asymptomatic progressive multifocal leukoencephalopathy and its subsequent treatment resulted in a benign clinical course. In consideration of the additional small number of cases of asymptomatic progressive multifocal leukoencephalopathy that have been reported, we conclude that routine magnetic resonance imaging surveillance is important for patients with multiple sclerosis who are at high risk for developing natalizumab-associated progressive multifocal leukoencephalopathy.