Non-mosaic Klinefelter syndrome with normal semen parameters and ability to conceive.

Background: Non-mosaic 47,XXY (Klinefelter syndrome, KS) males rarely retain preserved spermatogenesis. Here, we describe a 43-year-old man with intact fertility (prior natural conception, normal semen parameters), challenging conventional phenotypic paradigms.

Objectives: To report an exceptional non-mosaic 47,XXY case with preserved fertility and normozoospermia, redefining classic phenotyping norms.

Materials and methods: We conducted an observational study of a couple (male, non-mosaic 47,XXY; female, normal karyotype) undergoing two PGT-A cycles. Data included semen analyses, reproductive system ultrasonography, endocrine profiles, and embryo genetic diagnostics.

Results: Two PGT-A cycles using fresh/thawed sperm yielded three blastocysts: two aneuploid blastocysts in the first cycle (3BC; 6BC) and one untested blastocyst in the second cycle (4BC). Due to cost constraints, the patient declined euploidy testing in the second cycle. A thawed embryo transfer (FET) was performed with the untested blastocyst, resulting in no pregnancy.

Conclusion: This study presents a paradigm-shifting case of successful assisted reproduction in a couple where the male partner has non-mosaic KS with preserved fertility potential. Our findings challenge conventional assumptions about natural conception in KS patients and underscore the need for: (1) comprehensive evaluation of reproductive endocrine function, (2) molecular characterization of the testicular microenvironment, and (3) longitudinal assessment of fertility potential in atypical KS presentations.