Abstract Neurological complications post transplant have been described with the use of calcineurin inhibi- tors. Although tacrolimus may be a better immunosup- pressant than cyclosporine, its neurological side effects may be worse. Two children, living-related kidney trans- plant recipients, were treated with antibody induction, mycophenolate mofetil, prednisone, and tacrolimus. Soon after transplant, they each developed an encepha- lopathy, which when visualized by magnetic resonance imaging showed that it affected both white and grey mat- ter of the brain. Although the encephalopathy was asso- ciated with the use of tacrolimus, there was a complete neurological recovery without cessation of the drug. Keywords Encephalopathy · Tacrolimus · Grey matter · White matter · Transplantation Introduction Calcineurin inhibitors are an essential component of im- munosuppression in renal transplantation. In pediatric transplant recipients, tacrolimus has significant advanta- ges over cyclosporine (CsA) since its increased potency can lessen the amount of steroids required for immuno- suppression. This in turn has many benefits, including enhanced growth during childhood. However, some cen- ters have reported an increased risk of viral infections and lymphoproliferative disease post transplant with ta- crolimus [1, 2]. In addition, its neurological side effects may be worse than seen with CsA [3, 4]. Since February 1998, our immunosuppression proto- col has consisted of tacrolimus, mycophenolate mofetil (MMF), and prednisone. Previously, we used CsA, pred- nisone, and either MMF or azathioprine. In our current tacrolimus-based protocol, steroids are completely with- drawn between 6 and 9 months post transplant. In the 1st month post transplant, the target range for trough tacroli- mus levels, as measured in whole blood by enzyme- linked immunoassay, is 8–10 ng/ml. By 1 year, the dose of tacrolimus is decreased and target levels are 3–7ng/ml. MMF is initiated 1 day prior to transplant and adjusted according to gastrointestinal tolerance to a max- imum of 600 mg/m 2 per day. All patients receive anti- body induction, either with antithymocyte globulin (ATG) or daclizumab. We have not observed an increase in rejection epi- sodes or an increase in viral infections or lymphoprolif- erative disease as a result of our change in protocol [5]. However, 2 patients developed a transient encephalopa- thy associated with the use of tacrolimus soon after transplant. In both cases, the encephalopathy was man- aged by treatment of hypertension and fluid overload, which likely contributed to the neurological recovery. Tacrolimus therapy was not discontinued in either pa- tient despite these adverse events. Case reports Case 1 A 7-year-old male with renal failure secondary to dysplasia was receiving peritoneal dialysis at the time of his second transplant. He was first transplanted at 5.5 years, but developed post-trans- plant lymphoproliferative disorder involving the adenoids, liver, and spleen that necessitated withdrawal of immunosuppression, graft removal, and chemotherapy. At the time of his second trans- plant, he had been tumor free for 2 years, with no radiological evi- dence of disease, including by computerized tomography (CT) of the head. He received a living-related donor kidney (LRD) [donor: P. Parvex ( ✉ ) · L.E. Bell · I.R. Gupta Department of Pediatrics, Division of Nephrology, Montreal Children’s Hospital, McGill University, 2300 Tupper Street, E222, Montreal, Quebec H3H 1PS, Canada e-mail: pparvex@hotmail.com Tel.: +1-514-9344400, Fax: +1-514-9344478 A.M.G. O’Gorman · Y.G. Patenaude Department of Pediatrics, Division of Radiology, Montreal Children’s Hospital, McGill University, Montreal, Quebec, Canada M. Pinsk Department of Pediatrics, Izaak Walton Killam Hospital, Halifax, Nova Scotia, Canada Pediatr Nephrol (2001) 16:537–542 © IPNA 2001 TRANSPLANTATION / ORIGINAL ARTICLE P. Parvex · M. Pinsk · L.E. Bell · A.M.G. O’Gorman Y.G. Patenaude · I.R. Gupta Reversible encephalopathy associated with tacrolimus in pediatric renal transplants Received: 7 September 2000 / Revised: 2 January 2001 / Accepted: 30 January 2001