A previously healthy 39-year-old woman presented with confusion and aphasia. She rapidly became minimally conscious, only intermittently withdrawing to pain. CSF was unrevealing. MRI brain showed widespread subcortical and infratentorial T2 hyperintense lesions. After diagnosis of acute encephalitis, she was treated with IV steroids, 11 sessions of plasma exchange, and 5 sessions of IVIG with little to no clinical response. Further MR imaging revealed spinal cord and open ring-enhancing juxtacortical lesions. After ruling out alternative causes, she was diagnosed with Marburg variant MS and started on HiCy. As early as day two of treatment, she became alert and oriented and was consistently able to follow commands for the first time. She demonstrated steady clinical improvement thereafter, and was discharged with an EDSS of 1. At three-month followup, she had ongoing disability-free stability and started ocrelizumab for maintenance therapy.

Though rare and diagnostically elusive, early recognition of Marburg and initiation of rescue treatment with cyclophosphamide can be lifesaving. Given its many potential adverse reactions, the decision to use of HiCy should not be taken lightly and must be weighed against other treatment modalities. We propose that despite these risks, the risk of not treating or delaying treatment in the face of fulminant MS is far greater. This case represents the swiftest and most significant clinical recovery (EDSS 9 to 0) in a patient with Marburg MS treated with HiCy.