CSF3 and Posterior Leukoencephalopathy Syndrome: Other risk factors for PRES in children undergoing HSCT include hypomagnesaemia, acute GvHD (aGvHD), the use of umbilical cord blood as a stem cell source, the use of granulocyte colony-stimulating factor (G-CSF) and the use of fludarabine as part of the conditioning regimen (68, 69).