We report the first case of combined retinal and CNS varicella zoster-associated vasculitis in a 49-year-old patient with multiple sclerosis who had been treated with natalizumab. He presented with a progressive bilateral visual loss. The diagnosis of a vasculitis was based on the fundoscopic examination and MRI findings. We confirmed the varicella zoster virus (VZV) infection of the CNS by PCR and increased intrathecal antibody indices in the cerebrospinal fluid. The patient was stabilized with antiviral treatment, methylprednisolone, plasmapheresis and cycophosphamide. Natalizumab was discontinued. This case illustrates the neuroimmunological and neuroinfectiological consequences of treatments with biologicals that influence the immune system.