Improvement of progressive multifocal leukoencephalopathy after cidofovir therapy in a patient with a destructive polyarthritis

The human neurotropic JC virus (JCV) is responsible for progressive multifocal leukoencephalopathy (PML), an infectious demyelinating brain disease with major morbidity and mortality, usually refractory to treatment. We describe a PML in a 67-year-old woman with a destructive polyarthritis associated with anti-JO1 antibodies treated with corticosteroids. Although glucocorticoid therapy was maintained, administration of cidofovir improved the neurological condition. Our observation demonstrates the expanding clinical importance of JCV in systemic rheumatic diseases, particularly when immunosuppressive agents are used, and neurological symptoms or white matter changes on central nervous system imaging should arouse the suspicion of PML.