Mucosal damage leads to increased incidence of GI GVHD and is increased in patients receiving a myeloablative conditioning regimen (MAC) compared with those receiving a reduced intensity conditioning regimen (RIC). (A) Cumulative incidence of GI GVHD is increased in patients with more mucosal damage as measured by I-FABP levels below the median (27% vs 18% at 100 days, P = .0024). (B) I-FABP levels are lower at day 7 posttransplant in patients who received MAC vs RIC, which correlates with increased mucosal damage.