All mixed up?—genotype change after stem cell transplantation impeded verification of 21-year-old semen sample—a case report

We report a case of identity testing in which a patient charged us with the verification of a semen sample that he had donated and cryopreserved more than 20 years ago and now was suspecting of having been inadvertently interchanged. We found a non-match of the DNA profiles of the patient’s blood and the semen samples but could show that this was due to the patient having received a stem cell transplantation of his full brother as part of a cancer therapy in 1997 which was not known to us when the samples were first tested. Also, the blood and semen samples exhibited a low probability of full sibship at first supporting the patient’s suspicion that his semen sample might indeed have been interchanged. By also testing Y-STRs and including hair roots in the DNA analysis, we could show that the transplant did indeed originate from the patient’s brother and that the semen sample did indeed originate from the patient.