Phenotypic variability in Klinefelter syndrome: clinical findings including reported fatherhood
摘要
Klinefelter syndrome (KS) is the most common sex chromosome numerical abnormality in males and exhibits substantial heterogeneity in clinical, hormonal, and reproductive features. This study aimed to characterize the comorbidity profile, hormonal status, and anthropometric features of a mixed-age KS cohort and to contextualize the findings within current literature.
MethodsForty individuals diagnosed with cytogenetically confirmed KS between 2020 and 2025 were included in the study. Of these, 38 had classic KS and two had high-grade aneuploidy (HGA), which were analysed separately. The following were recorded: clinical characteristics; hormone profiles (follicle-stimulating hormone (FSH), luteinising hormone (LH), estradiol and testosterone); testicular volumes; and karyotype results. Semen analysis was only performed on adults and evaluated according to the 2020 World Health Organization criteria.
ResultsPediatric patients largely showed age-appropriate hormonal profiles with reduced testicular volumes. In adulthood, non-mosaic 47,XXY individuals typically exhibited hypergonadotropic hypogonadism and markedly reduced testicular volumes, whereas mosaic adults showed comparatively less pronounced endocrine alterations, based on descriptive observations. The majority of adult patients were azoospermic, and semen parameters were markedly impaired within the cohort. Given the retrospective design and cohort heterogeneity, all findings are presented descriptively. Repeated semen analyses showed preserved sperm concentration in three individuals with the 47,XXY karyotype; however, motility parameters were abnormal according to WHO 2020 criteria.
ConclusionKS patients exhibit significant age-related differences in terms of phenotype and hormones. Although gonadal function is largely preserved during childhood, the picture in adulthood is typically dominated by testicular insufficiency and impaired spermatogenesis. These observational findings emphasise the critical importance of early diagnosis, regular endocrine monitoring, and genetic counselling, including fertility preservation strategies, in the long-term management of these patients.