A study by Washington University of Medicine in St. Louis suggests that extremely rare, harmful genetic mutations present in healthy donor’s bone marrow aka stem cells, may be passed on to cancer patients receiving the transplants. It is possible that donor is not showing any sign of health problem due to these mutated stem cells.

The intense chemo and radiation therapy given the cancer patient prior to the transplant and the immunosuppression given thereafter, allow cells with these rare mutations a perfect environment to quickly replicate, thereby potentially creating health problems for the patients who receive them. The health concerns include heart damage, graft versus host disease, and possible new leukemia.

According to researchers the findings raises questions about the origins of some of the well-known side effects of stem cell transplants. Because the study was conducted on a small sample size, it was concluded, in general, that about half of all patients who receive stem cell transplants go on to develop some form of graft versus host disease.