What is the mortality rate typically associated with severe GVHD in HSCT patients?

In hematopoietic stem cell transplantation (HSCT) patients, severe graft-versus-host disease (GVHD) poses a significant risk and is associated with a high mortality rate. Severe GVHD can occur when the donor's immune cells attack the recipient's tissues, which can result in extensive damage to vital organs.

The mortality rate for severe GVHD is notably high, with estimates suggesting that in extreme or untreated cases, it can approach 100%. This makes severe GVHD one of the leading causes of morbidity and mortality in HSCT recipients. Even with aggressive treatment, such as immunosuppressive therapy, the outcomes can be poor, especially if the disease progresses to an advanced stage.

In contrast, the mortality rates associated with other options such as 30% survival or approximately 50% mortality suggest more favorable outcomes than what is seen in severe cases of GVHD. Additionally, the assertion of "no significant mortality risk" does not align with clinical observations, as severe GVHD is well-documented to lead to substantial risk of death. Thus, the option indicating up to 100% mortality in extreme cases accurately reflects the grave nature of severe GVHD in the context of HSCT patients.