A 37 year old male with myelodysplastic syndrome underwent a normal-appearing baseline brain MRI prior to bone marrow transplantation (BMT), which was nearly normal on FLAIR (A), DWI (B) and ADC map (C). Nineteen days post-BMT, while the patient was on cyclosporine therapy (an immunosuppressant medication), regions of hyperintensity (arrows) from ATL developed within the bilateral posterior PVWM on FLAIR (D) and DWI (E); note mild, asymmetric reduced diffusion in the left posterior PVWM on the ADC map (F, arrow). The patient’s symptoms promptly resolved over several days after the cessation of cyclosporine.