gastrointestinal illness. Exam was notable for flaccid quadriparesis, hyporeflexia without encephalopathy. He received IVIG for presumed Guillain Barre syndrome. Initial CSF analysis and MRI Brain/spine were unremarkable except high CSF lactate of 2.9. A week later, he became less responsive, had autonomic fluctuations, lost gag reflex, and got intubated. Repeat MRI Brain showed new bilateral (L>R) cortical, subcortical and brainstem lesions as seen in Figures 1A, 1B & 1C. Serial MRI brain showed fast developing multiple lesions involving the white and gray brain matter with areas of restricted diffusion. Repeat CSF analysis including encephalopathy/ multiple sclerosis panel were unremarkable. Biopsy of left frontal lesion showed vasculitis with lymphocytic infiltration and areas of small hemorrhage with no necrosis as shown in Figures 2A & 2B. He had no response to 7 days of IV steroids or IVIG. Cyclophosphamide therapy was started for presumed CNS vasculitis and mitochondrial cocktail for high serum/CSF lactate though rest of the mitochondrial labs returned negative. Infectious work up for Aspergillus, hepatitis B&C, Bartonellosis, Lyme, Tuberculosis and HIV were negative.