Posterior reversible encephalopathy syndrome (PRES) is a clinical and radiological entity linked to multiple aetiologies with similar neuroimaging findings. Its incidence is unknown, and its pathogenesis is multifactorial, encompassing phenomena of endothelial dysfunction and cerebral flow autoregulation, inter atia. There is a wide variety of associated conditions, the most frequent being hypertension, eclampsia, and immunosuppressive therapy, along with other drugs, autoimmune diseases, and even uraemia. We present the case of a reversible posterior encephalopathy syndrome secondary to renal involvement as a debut form of AL amyloidosis. (C) 2021 SEH-LELHA. Published by Elsevier Espana, S.L.U. All rights reserved.