A case of progressive multifocal leukoencephalopathy (PML) is described in an HIV-negative patient with mixed connective-tissue disease (MCTD) on a minimally immunosuppressive treatment with hydroxychloroquine. The patient presented with right-sided weakness, episodes of disorientation and loss of short-term memory and of vision in her right eye. PML was diagnosed by JCV DNA on cerebrospinal fluid and radiological criteria. She was treated with off-label maraviroc and mirtazapine but died two months after hospital admission, despite a surprising decrease in the viral load of cerebrospinal fluid three weeks after starting therapy. Prompt diagnosis and antiviral treatment of PML even in low-risk patients are warranted. Future studies are required to define the therapeutic role of maraviroc (MVC) and mirtazapine in this setting.