Progressive multifocal leukoencephalopathy: unusual MRI findings and prolonged survival in a pregnant woman.

We report a biopsy-proven case of progressive multifocal leukoencephalopathy (PML) in a pregnant woman without obvious underlying immune disorder. MRI showed lesion enhancement and deep gray matter involvement, which are uncommon imaging patterns in PML. The clinical course in this case is also rather atypical, as the patient is alive 16 months after disease onset. The combination of these unusual characteristics in PML is unknown and indicates that the criteria for this disease may need to be redefined.