Nevada cancer survivor found to have two different sets of DNA after bone marrow transplant 4 years ago

The procedure had replaced the patient's blood DNA with that of his donor. The foreign DNA managed to find its way into the patient's cheeks, lips and semen.

                            Nevada cancer survivor found to have two different sets of DNA after bone marrow transplant 4 years ago
(Source : Getty Images)

A Nevada man suffering from Leukemia received a bone marrow transplant from a donor, four years ago. Now, he has discovered he is a chimera: a rare condition where people live with two sets of DNA in their body.

The man named Chris Long, who works at the Washoe County sheriff's office in Nevada, learned of his condition after undergoing genetic tests, thanks to his colleagues from the forensics unit. "I thought that it was pretty incredible that I can disappear and someone else can appear," Long told The New York Times.

The procedure had replaced his blood DNA with that of his donor's. This is on expected lines, say experts. After bone marrow transplantation, patients have the donor's DNA in their blood.

But what left Long and his colleagues puzzled was the extent of infiltration in his body. The test revealed that the donor's DNA found its way into Long's cheeks, lips and semen.

"Any place blood cells can traffic could have traces of donor DNA present. The donor DNA, however, should not be the dominant DNA present in those other body areas," Dr. Timothy Fenske, Medical College of Wisconsin, told MEA WorldWide (MEAWW).

Patients who undergo the procedure are expected to have their own DNA in the vast majority of their cells. "We were kind of shocked that Chris was no longer present at all," Darby Stienmetz, Long’s colleague told the New York Times.

However, Long has retained his DNA in the hair on his head and chest, where it has remained entirely unchanged. 

Furthermore, according to experts, foreign DNA does not interfere with a person's identity. "Their brain and their personality should remain the same," Dr. Andrew Rezvani, the medical director of the inpatient Blood & Marrow Transplant Unit at Stanford University Medical Center, told the New York Times.

Neither will chimera's like Long pass on the donor's DNA into their future offspring, according to bone marrow transplant experts. "There shouldn't be any way for someone to father someone else's child," added Dr. Rezvani. 

"I know of no evidence that marrow or blood stem cell transplantation could lead to chimerism in the actual sperm or eggs – that would make no sense really. There must have been traces of DNA in the semen (semen is mostly prostatic fluid and not the same as sperm)," Freske told MEAWW.

Long's case could open up questions on the reliability of DNA tests — which are considered unquestionable evidence — during criminal investigations. When dealing with chimera's like Long, DNA tests could mislead investigations, said experts.

Nearly 23,000 bone marrow or umbilical cord blood transplants were performed in the US in 2017. And if one among them responded similarly to a transplant and that person went on to commit a crime, it could mislead investigators, according to Brittney Chilton, a criminalist at the Sheriff's Office forensic science division.

A case in point is one in Alaska. In 2004, investigators in Alaska recovered traces of DNA from a crime scene, which matched a profile on a criminal DNA database.

However, the match was to a man who was already in prison at the time of the assault. Later, the investigators realized that this man received a bone marrow transplant from his brother, who was eventually convicted.
Scientists say that Long is a living, breathing case study of one, and it's impossible to say how many other people respond to bone marrow transplants the same way he did.

It is simply one of those curious possibilities that forensic analysts may want to consider when DNA results are not adding up, said people who have reviewed Long's case, as reported by The New York Times.

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