Factors occurring before and during hematopoietic stem cell transplantation may lead to dysbiosis and potentially significant long-term sequelae. Figure 5D, in the article by Goncalves et al that begins on page 2585, showing decreased bacterial diversity, has been incorporated into the figure. GC, gamma chain SCID; HC, healthy control; IgRT, immunoglobulin replacement therapy. Professional illustration by Somersault18:24.