Research Effect of Age on Leukopenia Following Renal Transplantation at a Single Center Yanmen Yang, PharmD 1 , Christina M. Guerra, PharmD, BCPS 2,3 , and Nabil Sumrani, MD 4 Abstract Introduction: Leukopenia in renal transplant recipients occurs commonly within the first year following transplantation; however, literature on the effects of age on leukopenia is scarce. Design: A single-center, retrospective review was conducted on 141 recipients transplanted from January 2011 to December 2015. Transplant recipients were characterized by age <60 years (n ¼ 94) or age 60 years and older (n ¼ 47) for analysis. Results: A greater incidence of leukopenia was seen in the older cohort compared to the younger cohort (64% vs 55%). Of those patients who developed leukopenia, the older cohort (n ¼ 30) had a higher incidence of hospitalization for leukopenia (30% vs 23%) but a lower incidence of hospitalization for infection (20% vs 25%) compared to the younger cohort (n ¼ 52). Additionally, one month following mycophenolate mofetil (MMF) discontinuation, the older cohort had reduced recovery of their white blood cell count (þ263.8% vs þ272.5%) and experienced less recurrent leukopenic episodes (50% vs 67%) and rejection episodes (0% vs 22%) compared to the younger cohort, alluding to the need for less immunosuppression. Conclusions: Age at transplantation was not associated with the development of leukopenia; however, older patients had a higher incidence of leukopenia and hospitalization for leukopenia. Dose reduction or discontinuation of MMF should be considered in older kidney transplant recipients who develop leukopenia. Keywords kidney transplantation, leukopenia, mycophenolate mofetil, immunosuppression, immunosenescence Introduction Renal transplantation has become more common in older patients due to the increasing average age of patients with end-stage renal disease. 1 Over the past ten years, the proportion of waitlisted candidates aged 65 years and older has increased from 14.5% in 2005 to 22% in 2015. 2 An aging transplant recipient population can lead to challenges in prolonging patient and allograft survival, particularly the added difficulty of factoring in age-related declines in the immune system when balancing the risks of both under- and overimmunosuppression. Known as immunosenescence, this decline in immune function over time affects both the innate and the adaptive immune systems but appears to have the greatest impact on cellular immunity. 3 Leukopenia, or the abnormal reduction in white blood cells, is a major concern as it reduces the body’s immune defenses and increases the risk of developing infections. As a result, elderly patients are inherently at risk of leukopenia and, subsequently, infections. 4 Although infection has been reported as one of the most common causes of death following trans- plantation, the literature on the effects of age on leukopenia after transplantation is scarce. 3,5 In addition to immunosenescence, commonly used medica- tions crucial to the success of transplantation are known to increase the risk of leukopenia, including rabbit antithymocyte globulin (rATG), mycophenolate mofetil or sodium (MMF or MPS), and valganciclovir (VAL). A polyclonal antibody, rATG, is used for induction of immunosuppressive therapy peri- and posttransplantation. Although observational data show rATG reduces both preformed and de novo donor- specific antibodies, it exerts its main immunosuppressive effect through complement-dependent cell lysis and T-lymphocyte depletion. 6-8 Mycophenolate, an antiproliferative agent used for its immunosuppressive effects to prevent rejection, can lead to leukopenia through interference with guanosine and deoxy- guanosine nucleotide production, which is necessary for T- and B-lymphocyte differentiation. 9 Valganciclovir, the ester 1 Department of Pharmacy, SUNY Downstate Medical Center, Brooklyn, NY, USA 2 Department of Pharmacy Practice, University of the Incarnate Word Feik School of Pharmacy, San Antonio, TX, USA 3 Department of Surgery, Transplant Center, University of Texas Health Science Center, San Antonio, TX, USA 4 Department of Transplant, SUNY Downstate Medical Center, Brooklyn, NY, USA Corresponding Author: Yanmen Yang, Department of Pharmacy, SUNY Downstate Medical Center, 450 Clarkson Avenue, Brooklyn, NY 11203, USA. Email: yangyanm01@gmail.com Progress in Transplantation 2019, Vol. 29(1) 54-60 ª 2018, NATCO. All rights reserved. Article reuse guidelines: sagepub.com/journals-permissions DOI: 10.1177/1526924818817017 journals.sagepub.com/home/pit