A decade of excellent transplant survival in children with inherited metabolic diseases: A report from a single metabolic transplant centre in Europe

Hematopoietic cell transplantation (HCT) confers a long-term disease-modifying therapy for transplant-permissive inherited metabolic diseases (IMDs). We examined the overall survival (OS) and engrafted survival (ES) of children with IMDs, who received first HCT at Royal Manchester Children's hospital from 1985 to 2016. A total of 137 children with IMDs were included in this analysis (historical cohort [1985-2006], n＝65; current cohort [2007-2016], n＝72). Primary diagnoses included mucopolysaccharidoses (81%), X-linked adrenoleukodystrophy (6%), metachromatic leukodystrophy (4%), mannosidosis (3%), Wolman disease (2%), and other conditions (4%). The five-year OS has increased from 65% (95% confidence interval [CI], 52%-76%) in the historical cohort to 91% (95% CI, 81%-96%) in the current cohort (P<0.001). Moreover, the five-year ES, which was 64% (95 CI%, 56%-72%) for the entire cohort, has doubled from 41% (95% CI, 29%-53%) in the historical cohort to 85% (95% CI, 75%-92%) in the current cohort (P<0.001). The proportion of patients with graft failure has decreased from 37% in the historical cohort to 8% in the current cohort (P<0.001). In patients who received a second transplant, 13 out of 20 patients (65%) in the historical cohort and all four in the current cohort were alive and engrafted. Of 82 survivors followed-up at Manchester, 80% and 20% had full and mixed chimerism, respectively. Although this study was restricted to a single center, our findings show that HCT is an increasingly safe procedure and provides long-lasting endogenous enzyme replacement therapy for children with IMDs in the modern era of HCT.