Microbes matter in pediatric allo-HSCT.

In this issue of Blood, Masetti et al(1) report on the findings of a multicenter observational study that explored the role of the microbiome in pediatric allogeneic hematopoietic stem cell transplantation (allo-HSCT). They studied 90 children and found that patients with high fecal microbial diversity prior to allo-HSCT had longer overall survival and a lower incidence of acute graft-versus-host disease (GVHD) compared to patients with low microbial diversity. In adult allo-HSCT recipients, high pretransplant fecal diversity has also been positively correlated with overall survival. Importantly, a key difference between this pediatric study and prior analyses in adults is that in this work, the perineutrophil-engraftment microbiome was not associated with outcome, whereas intestinal microbial features during this time window have been shown to predict outcome in adults (see figure).