Chromosome Y as a marker for sex discrepancies in patients with organ transplants: a case report

BACKGROUND: Organ transplantations cause discrepancy in results from cell-free DNA (cfDNA) testing, but scientific literature is scarce. CASE: A 33-year old gravida underwent cfDNA testing, which showed high levels of Y chromosome (ChrY) in the maternal bloodstream. The ChrY pattern was comparable to an adult male reference. As a result, cfDNA testing was only informative for autosomes. Routine 20-week ultrasound scan showed no structural alterations and the presence of female external genitalia. Post-clinical research revealed that the patient received a bone marrow transplant from a male donor several years before. Fluorescence in situ hybridization showed that 100% of nuclei analysed from the patient’s lymphocytes presented a ChrY. CONCLUSION: This case demonstrates ChrY can be used as a marker to avoid sex discrepancies in certain patients with organ transplants.