*Purpose: There are a growing number of pediatric (peds) patients (pts) awaiting renal transplantation (tx) who are considered highly sensitized (HS). We report long-term outcomes of desensitization (des) in HS peds tx recipients.

*Methods: HS peds renal tx performed between 1/2009 and 6/2019 were evaluated. HS was defined as calculated panel reactive antibody (cPRA) >30%. Pts underwent des with IVIG +/- plasmapheresis, rituximab, and/or Tocilizumab (added after 2013). All pts received alemtuzumab induction (15-30mg SQ at time of tx) and were on tacrolimus, mycophenolate and steroids. Pts were evaluated for cPRA prior to, and following des, HLA mismatch, and DSA. Serum creatinine (sCr), rejection, pts and graft survival (GS) were evaluated.

*Results: 23 HS peds pts underwent des. Sensitizing events included prior tx (n=20, 87.0%), transfusion (n=9, 39.1%. 2 pts(8.7%) had no obvious sensitizing event. The peak cPRA was 74 (interquartile range, IQR= 49-90). Most pts were desensitized using IVIG and rituximab (86.9%); three (13.0%) with plasmapheresis, IVIG, and tocilizumab. Nine (39.1%) received more than one round of des. Only 6(26.1%) showed decrease in cPRA after treatment (mean change -22.6% ± 10.1%). Median time between dialysis and des was 1091 days(691-1744), and between des and tx was 207 days (IQR 64-445). 4(17.4%) received a living donor kidney tx. All pts had at least 2 HLA mismatches. B-cell (BCFCMX) and T-cell flow crossmatches (TCFCMX) at tx were 156 MCS (104-189) and 39 MCS (8-99) respectively (acceptable BCFCMX and TCFCMX<250 MCS). 13(56.5%) had preformed DSA at tx and 6(25.8%) developed de novo DSA. 2 tx (8.7%) had delayed graft function; median sCr at discharge was 0.9 (IQR 0.5-1.7). Over median 1721 days of follow-up, 14(60.8%) had rejection, 9 were within 1 year of transplant. Five (26.3%) showed ABMR, 7 (36.8%) with TCMR and 2 (10.5%) had both. Of pts with rejection, 9 (69.2%) had preformed DSA and 6(50%) developed de novo DSA. One-year graft survival was 91.3% while overall, 4 (17.4%) experienced graft loss during follow up: 1 from CMV disease, 1 recurrent FSGS and 2 ABMR. One pt died at 2217 days post-tx.

*Conclusions: Desensitization therapy does not significantly change cPRA scores but can result in acceptable crossmatch and decreased wait time for HS peds pts with ESRD. Use of T-cell depleting agents for induction allows for feasible renal tx. While rejection remains a serious concern with preformed DSA as a primary risk factor, 1-year GS is acceptable. Continued utilization will provide additional information for analysis and promotion of desensitization in this population.

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