Posted on Dec 23, 2019, 3 p.m.
Chris Long of Reno, Nevada is currently in remission from acute myeloid leukemia. Just three months after undergoing bone marrow transplant operation it was revealed that the DNA in his blood had changed.
Four years after his bone marrow transplant operation it was discovered that parts of his tongue, cheeks and lips all contained his donor’s DNA; his head and chest hair appear to be the only parts not affected based on sample testing results. Of more concern all of the DNA in his semen were discovered to belong to his donor. Technically this means that Long is now a chimera as he now has two sets of DNA, one of his own and the other from his German transplant donor.
“This is not much of a surprise,”said Dr James Davies from the Medical Research Council Weatherall Institute of Molecular Medicine at the University of Oxford. “We actually struggle to get pure samples of host DNA from these patients because immune cells infiltrate virtually all tissues.”
According to Davies, “The finding in sperm superficially seems interesting until you realise that the man had a vasectomy. Thus what is being analysed as "sperm" doesn’t actually contain any sperm and it is contamination with donor lymphocytes that are being detected. It is very important to highlight that it is impossible for the patient to father a child with the donor's DNA.”
Long works at the Washoe County Sheriff’s Department where one of his colleagues had encouraged him to test his blood to see what changes may occur, but no one was expecting to see the surprising extent of the results. “We were kind of shocked that Chris was no longer present at all,” said Darby Stienmetz, a criminalist at the Sheriff’s office.
The procedure is said not to change a person’s personality, but there can be repercussions such as that of Long, of having your DNA change, and some criminal cases have already been affected by the phenomenon such as a DNA profile taken in 2004 from a potential suspect being traced to a man who was in prison at the time the assault took place; later it was learned the man had received a bone marrow transplant from his brother, and eventually he was convicted of the crime.
In another case, a woman claimed she was the victim of sexual assault by one man, but investigators were skeptical as DNA analysis showed there were two, until the second profile was found to be that of her bone marrow transplant donor.
Another woman almost had her children removed from her custody after government testing required for applying for assistance showed she was not their mother until extensive testing revealed that she too was a chimera after having a transplant.
Tens of thousands of people undergo transplants for leukemia, lymphoma, blood cancers, and sickle cell anemia every year. Typically this is a good thing as it is lifesaving, but when you take in the full scope there is the possibility for many things to go wrong, such as any of these patients could commit a crime, be the victim of one, or receive a transplant from a donor who was, and this could create some life changing confusion if DNA testing is relied upon.
Long’s case was presented at an international conference for forensic science this year as criminal investigators typically work under the assumption that both victims and criminals leave behind DNA code which they can be identified by, and yet people who have had a transplant now have two, and one of the set could well belong to someone who had no actual involvement in the incident.
While Long is very grateful for the donation and has plans to travel to Germany to personally thank the donor in person his story brings light to a series of interesting questions about DNA and human identity.
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