What is she doing here? Klinefelter syndrome in forensic casework

•Seminal fluid from a sexually assaulted male victim did not contain sperm cells following specific staining and microscopic screening.•DNA Profiling results from the non-sperm cell fraction of the seminal fluid showed a major/minor DNA mixture that could be interpreted as from a female and male.•A reference sample from the victim, showed an imbalance between the X and Y chromosomes.•Evidence of two X chromosomes detected using the The QIAGEN Investigator® Argus X-12 kit suggested that the victim was likely to have Klinefelter syndrome. In this case report, we describe a sexual assault incident in which the male victim’s seminal fluid contained no sperm cells, as indicated by sperm cell staining and microscopic screening, and DNA profiling results from the non-sperm cell fraction showed a major/minor DNA mixture that could be interpreted as female and male. DNA profiling of a sample from a disposable drinking cup used by the victim at the crime scene provided a single source profile, and showed a 2:1 imbalance between the heights of the X and Y chromosomes, respectively. The victim’s DNA reference sample showed a similar imbalance of the X and Y chromosomes. These observations suggested that the victim might suffer from Klinefelter syndrome, a genetic disorder related to the sex chromosomes. Here, we describe the first reported use of the QIAGEN Investigator® Argus X-12 kit for characterization of X-chromosomal STR loci to potentially identify a case of Klinefelter syndrome. This commercially available kit is primarily used in forensic laboratories to investigate kinship relations and for paternity testing in alleged father/daughter cases. Results of the X chromosome DNA profiling from the victim’s disposable drinking cup and reference samples revealed two alleles at various X-chromosomal STR loci. Moreover, this kit can also amplify a Y chromosome specific sequence (AMEL-Y), and the results indicated that this sample actually originated from a male. Evidence of two X chromosomes in the victim's DNA suggested that he was likely to have Klinefelter syndrome. In this case report, we propose the use of the QIAGEN Investigator® Argus X-12 kit as a practical forensic tool for the detection of potential genetic syndromes related to the sex chromosomes, which can affect test results and, at times, make them difficult to interpret. We also aim to increase awareness within the forensic science community regarding the existence of genetic anomalies, which should be