Unusual Case of Progressive Multifocal Leukoencephalopathy in a Patient With Sjögren Syndrome.

Progressive multifocal leukoencephalopathy (PML) is a rare demyelinating disease caused by reactivation of John Cunningham virus affecting typically subcortical and periventricular white matter of immunocompromised hosts (human immunodeficiency virus infection, hematologic malignancies). Cerebral hemispheric white matter is most commonly affected by lytic infections, leading to progressive damage to oligodendrocytes in the central nervous system. Neuroimaging usually highlights scattered foci of white matter hypodensity not attributable to contrast enhancement or mass effect. In contrast, we present an unusual case of PML predominantly affecting cervical spinal cord and brainstem in an immunocompetent host. This is a rare subset of PML case that can occur in association with connective tissue disorders (Sjögren Syndrome in this case), systemic lupus erythematosus being the most common. Progressive multifocal leukoencephalopathy should be considered in the differential diagnosis of spinal cord or brainstem lesions, particularly in the patients with connective tissue disorders.