Mysterious and Shocking: After receiving a bone marrow transplant, a patient's seminal fluid contains only the donor's DNA

Four years ago, Chris Long, a computer scientist from Reno, Navada, received a bone marrow transplant from a European foreign donor. At the time, he did not suspect that it could have an unexpected impact: his seminal fluid is now that of the donor, containing only the DNA of the latter.

According to an article in The New York Times, the purpose of the transplant was to treat acute myeloid leukemia , a type of cancer that prevents the body from producing blood normally.

After the procedure, the donor's healthy hematopoietic cells replaced the damaged Long cells, allowing his body to resume normal blood production. It is therefore logical that Long's blood also contains the DNA of his donor.

Guinea pig…
But a colleague of Long (who works at the Washoe County Sheriff's Office), Renee Romero, who runs the office's forensic lab, suggested that bone marrow transplants could affect DNA elsewhere in her body. She had therefore encouraged Long to take DNA samples before the procedure so that the team could compare them to the post-operative samples. In other words, the office team wanted to use Long as a guinea pig (of course, after acceptance by him).

Since then, the sheriff's office team has collected many more DNA samples from various parts of the body, and at regular intervals over the years.

After analysis, they were able to identify both Long's DNA and that of its donor in some samples, including from his lips, cheeks and tongue (saliva). The samples taken from his chest and hair, in turn, reveal only the DNA of Long.

What was surprising for everyone is that four years after the procedure, Long's seminal fluid samples only reveal his donor's DNA, whereas a year later his semen contained both DNA. " I think it's pretty unbelievable that I can disappear and someone else can appear ..., " Long told NYT.

As the image on the computer screen shows, four years after the bone marrow transplant, Long's seminal fluid contains 100% of his donor's DNA, compared to 64% a year later. Credits: Tiffany Brown Anderson / The New York Times

Three bone marrow transplant experts, interviewed by the NYT, all agreed that it is normally impossible in such a procedure for a recipient to produce seminal fluid containing the donor's DNA.

But Mehrdad Abedi, the doctor who treated Long at the University of California at Davis, said the surprising seminal fluid of his patient was probably due to the fact that he had a vasectomy after the birth of his second child. However, the mechanism behind this seminal fluid DNA change remains mysterious.

Yet Long's situation raises all sorts of new questions about the use of DNA as evidence in court cases. Forensic scientists and forensic scientists now need to address the issue of the DNA of innocent people appearing at crime scenes because of bone marrow transplants.

If someone in Long's situation commits a sexual crime and the investigators collect seminal fluid samples, the bone marrow donor could be charged with the crime in the absence of any other DNA on the scene ... A comparison of DNA from several parts of the accused's body would therefore be necessary. A special case that the police must now consider.


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