Transplantation-associated thrombotic microangiopathy (TA-TMA) is a known complication of autologous hematopoietic cell
transplantation (aHCT), particularly in children with neuroblastoma. We describe a pediatric single-institution experience of
TA-TMA after aHCT. Data were abstracted from the medical record of patients who underwent aHCT between January 1, 2008, and July
1,2018, at Boston Children’s Hospital. TA-TMA was diagnosed using either the International Working Group criteria or the
“probable TA-TMA criteria” of Cho et al. Overall, 318 aHCTs were performed in 243 patients. Nine patients (3.7%)
were diagnosed with TA-TMA. TA-TMA occurred most frequently in children with neuroblastoma (n = 7; 78%), all of whom were
conditioned with carboplatin, etoposide, and melphalan. The median age at aHCT in children who developed TA-TMA was 3 years, 5
months (range, 18 months to 25 years). TMA was diagnosed at a median of 35 days (range, 8 to 106 days) after stem cell infusion.
On a retrospective chart review using the same criteria used by the provider, patients met criteria a median of 5 days before the
clinical diagnosis (range, 0 to 58 days). Eight patients had renal involvement at presentation, including nephrotic range
proteinuria and severe hypertension, requiring from 2 to 6 antihypertensive medications. Two patients presented with multiorgan
failure. Six patients were treated with eculizumab a median of 0 days after TA-TMA diagnosis (range, 0 to 11 days). On
retrospective review, patients were treated a median of 18 days (range, 0 to 58 days) after meeting criteria for TA-TMA. Before
initiation of therapy, 4 of 6 patients checked for serum complement levels had normal values, 1 had elevated CH50 and 1 had
elevated sC59-b and CH50. All patients had CH50 levels within the target range (≤3 CAE) after induction therapy. Two
patients (33%) had no response to eculizumab and died of multiorgan failure. The other 4 had both a hematologic response with
transfusion independence (median, 6.5 weeks; range, 4 to 9 weeks) and renal response, defined as resolution of nephrotic range
proteinuria (median, 21 weeks; range, 13 to 25 weeks). Among the eculizumab-treated survivors, 2 patients remained on prolonged
eculizumab therapy, and one had recurrence of TA-TMA after discontinuation of eculizumab. All 4 eculizumab treated survivors have
persistent organ dysfunction. Three children were treated with supportive care only; 2 died of relapsed cancer, and the third is
alive with stage 2 chronic kidney disease. The median duration of follow-up after TA-TMA diagnosis was 2.5 years (range, 9 months
to 4 years). The 1-year overall survival was 78% (SE = 14%). However, regardless of treatment, no survivors had complete
normalization of function in all organs. Two children with normal serum CH50 and sc5b-9 levels responded to eculizumab. This
report highlights the importance of maintaining a high suspicion for TA-TMA after aHCT. Further study is warranted to identify
individual risk factors for TMA after aHCT, predict the response to ec...