Myoung Uk Kim, M.D.1, Sae Yoon Kim, M.D.1, Su Min Son, M.D.2, and Yong Hoon Park, M.D.1 Department of Pediatrics1, Department of Physical Medicine & Rehabilitation2, College of Medicine, Yeungnam University, Daegu, Korea Received: 15 September 2010, Revised: 5 October 2010 Accepted: 20 October 2010 Corresponding author: Yong Hoon Park, M.D. Department of Pediatrics, College of Medicine, Yeungnam University, Daemyeong 5-dong, Namgu, Daegu 705-717, Korea Tel: +82.53- 620-3532, Fax: +82.53- 629-2292 E-mail: yhpark@med.yu.ac.kr We present a case of tacrolimus-induced encephalopathy after successful kidney transplantation. An 11-year-old girl presented with sudden onset of neurologic symptoms, hypertension, and psychiatric symptoms, with normal kidney function, after kidney transplantation. The symptoms improved after cessation of tacrolimus. Magnetic resonance imaging (MRI) showed acute infarction of the middle cerebral artery (MCA) territory in the right frontal lobe. Three days later, she had normal mental function and maintained normal blood pressure with left hemiparesis. Follow-up MRI was performed on D19, showing new infarct lesions at both cerebral hemispheres. Ten days later, MRI showed further improvement, but brain single photon emission computed tomography (SPECT) showed mild reduction of uptake in both the anterior cingulate gyrus and the left thalamus. One month after onset of symptoms, angiography showed complete resolution of stenosis. However, presenting as a mild fine motor disability of both hands and mild dysarthria, what had been atrophy at both centrum semiovale at 4 months now showed progression to encephalomalacia. There are two points of interest in this case. First, encephalopathy occurred after administration of tacrolimus and improved after discontinuation of the drug. Second, the development of right-side hemiplegia could not be explained by conventional MRI; but through diffusion tensor imaging (DTI) and diffusion tensor tractography (DTT) of white matter tract, visualization was possible. Case report DOI: 10.3345/kjp.2011.54.1.40 Korean J Pediatr 2011;54(1):40-44 A case of tacrolimus-induced encephalopathy after kidney transplantation Copyright © 2011 by The Korean Pediatric Society This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by- nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Key words: Tacrolimus, Encephalopathy, Kidney, Transplantation, Tractography, Child Introduction Cyclosporin A and tacrolimus are important immunosuppressant drugs used to prevent rejection of transplanted organs or bone marrow1). However, development of posterior reversible encephalophathy syndrome (PRES) is commonly seen in association with cyclosporin A and tacrolimus after transplantation1). PRES is a relatively new clinicoradiological entity first described as reversible posterior leu- koencephalopathy syndrome in 1996, characterized by headaches, altered mental status, seizures, and visual loss. Clinical neuroimaging 40