After a donor stem cell transplant, the donor’s stem cells (the graft) may sometimes react against your own cells (the host). This is called graft versus host disease (GVHD). It happens when the donor’s cells, usually a white blood cell (called a T-lymphocyte or T-cell) attack your body's cells.
GVHD does not mean the transplant has failed, and it can even have benefit. The donor cells may also attack any cancer or leukaemia cells that survived the conditioning treatment.
There are two forms of GVHD:
- Acute GVHD – usually develops within the first 100 days (about three months) after transplant but it may also happen after this time.
- Chronic GVHD – can start on its own a few months after transplant. Or, it can sometimes progress from the acute type.
The risk is linked with how closely you and your donor match. People who have unrelated or mismatched donors, or have had a donor lymphocyte infusion, are more at risk.
The effects of GVHD are usually mild. But in some people they can be severe and even life-threatening. It mainly affects the skin, mouth, stomach, bowel and liver.