Graft-versus-host disease (GVHD) is a possible complication after a donor stem cell transplant, when donor immune cells attack healthy tissues and organs. GVHD can be acute or chronic, and chronic GVHD (cGVHD) often develops after the first 100 days.

Because it's hard to predict who will develop cGVHD or how serious it may become, reaching the 100-day milestone is an important reminder to watch for new or changing symptoms and keep your care team informed of any changes.