An observational study in Klinefelter Syndrome (47, XXY), Sex Chromosome Aneuploidy and Disorders of Sex Development (DSD), sponsored by Université Paris-Saclay. Completed at 1 site in France. Open to male participants. Per ClinicalTrials.gov, last updated 2026-10-21.
Sponsored by Université Paris-Saclay · Observational
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Mosaic sex chromosome aneuploidy 47,XXY/46,XX is an exceptionally rare variant within the spectrum of Klinefelter syndrome. Available data remain limited, especially regarding adult phenotype and long-term characteristics, and no robust comparative data with non-mosaic 47,XXY Klinefelter syndrome are currently available. This retrospective monocentric comparative study is designed to describe the clinical, biochemical, cytogenetic, gonadal, anthropometric, and socio-professional characteristics of adults with 47,XXY/46,XX mosaicism. In addition, the study is intended to compare these characteristics with those of a homogeneous cohort of individuals with non-mosaic 47,XXY Klinefelter syndrome and with previously published case reports, in order to improve phenotypic characterization of this rare chromosomal condition.
47 studies on the registry are indexed under Klinefelter Syndrome; 17 are open to participants now.
This study's enrollment of 257 is below the median of 300 across 27 observational studies indexed under Klinefelter Syndrome.
Browse Klinefelter Syndrome studies →Université Paris-Saclay is the lead sponsor of 2 studies on the registry; 1 is open to participants now.
Counted across the registry records on this site, refreshed daily.
patients with a diagnosis of 46,XX/47,XXY mosaicism (mKS-XX) confirmed by cytogenetic assessments
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Group A (mKS-XX):
Group B (non-mosaic KS):
Exclusion Criteria:
Individuals with 46,XX/47,XXY mosaic formula Collection of clinical, demographic, anthropometric, socio-professional, hormonal and cytogenetic parameters characteristics whenever available
Individuals with homogeneous 47,XXY mosaic formula Collection of clinical, demographic, anthropometric, socio-professional, hormonal and cytogenetic parameters characteristics whenever available
Distribution of primary gonadal phenotype in patients with 46,XX/47,XXY mosaicism
number and percentage of participants according to primary gonadal phenotype: * bilateral testicles * unilateral testicles * unilateral ovary * unilateral or bilateral ovotestis
Time frame: Baseline
Correlation between XX cell-line percentage and final height within the mKS-XX cohort
Spearman's rank correlation analysis assessing the correlation between the percentage of 46,XX cells and final adult height. The percentage of 46,XX cells (%) was determined by conventional cytogenetic karyotyping, supplemented by fluorescence in situ hybridization (FISH) when available. Final adult height was obtained from clinical records and defined by a difference of less than 1 cm between two consecutive height measurements at least 6 months apart. Final height will be reported in meters. The correlation coefficient is dimensionless. Time Frame: Baseline
Time frame: Baseline
Between-group difference in adult height (mKS-XX vs non-mosaic KS)
Comparison of adult height between patients with mKS-XX and patients with non-mosaic Klinefelter syndrome, using the most recent available assessment at study inclusion. Adult height will be reported in meters.
Time frame: Baseline
Between-group difference in body mass index (mKS-XX vs non-mosaic KS)
Comparison of body mass index between patients with 46,XX/47,XXY mosaicism and patients with non-mosaic Klinefelter syndrome, using the most recent available assessment at study inclusion. BMI will be reported in kg/m².
Time frame: Baseline
Between-group difference in gonadal phenotype (mKS-XX vs non-mosaic KS)
Comparison of gonadal phenotype between patients with 46,XX/47,XXY mosaicism and patients with non-mosaic Klinefelter syndrome. Gonadal phenotype will include the presence of DSD and ovarian or ovotesticular tissue and will be reported as number and percentage of participants.
Time frame: Baseline
Between-group difference in testicular volume (mKS-XX vs non-mosaic KS)
Comparison of testicular volume between patients with 46,XX/47,XXY mosaicism and patients with non-mosaic Klinefelter syndrome, using the most recent available assessment at study inclusion. Testicular volume will be reported in mL.
Time frame: Baseline
Between-group difference in LH levels (mKS-XX vs non-mosaic KS)
Comparison of serum luteinizing hormone levels between patients with 46,XX/47,XXY mosaicism and patients with non-mosaic Klinefelter syndrome, using the most recent available measurement at study inclusion. LH will be reported in IU/L.
Time frame: Baseline
Between-group difference in FSH levels (mKS-XX vs non-mosaic KS)
Comparison of serum follicle-stimulating hormone levels between patients with 46,XX/47,XXY mosaicism and patients with non-mosaic Klinefelter syndrome, using the most recent available measurement at study inclusion. FSH will be reported in IU/L.
Time frame: Baseline
Between-group difference in testosterone levels (mKS-XX vs non-mosaic KS)
Comparison of serum testosterone levels between patients with 46,XX/47,XXY mosaicism and patients with non-mosaic Klinefelter syndrome, using the most recent available measurement at study inclusion. Testosterone will be reported in ng/mL.
Time frame: Baseline
Between-group difference in educational level (mKS-XX vs non-mosaic KS)
Comparison of educational level between patients with 46,XX/47,XXY mosaicism and patients with non-mosaic Klinefelter syndrome. Educational level was assessed from medical records according to the French and Belgian educational systems, using four categories: illiterate/no schooling, CAP/BAC, professional training, and bachelor's degree or higher. Results will be reported as numbers and percentages of participants in each category.
Time frame: Baseline
Correlation between XX cell-line percentage and delta height within the mKS-XX cohort
Spearman's rank correlation analysis assessing the correlation between the percentage of 46,XX cells and delta height. The percentage of 46,XX cells (%) was determined by conventional cytogenetic karyotyping, supplemented by FISH when available. Delta height was defined as the difference between final adult height and mid-parental target height, calculated using the Tanner formula. Delta height will be reported in meters. The correlation coefficient is dimensionless.
Time frame: Baseline
Correlation between XX cell-line percentage and educational level within the mKS-XX cohort
Spearman's rank correlation analysis assessing the correlation between the percentage of 46,XX cells and educational level. The percentage of 46,XX cells (%) was determined by conventional cytogenetic karyotyping, supplemented by FISH when available. Educational level was obtained from medical records and assessed according to the French and Belgian educational systems, using categories of educational attainment. Educational level is a categorical variable, and the correlation coefficient is dimensionless.
Time frame: Baseline
Plan to share: Undecided — Delicate findings, very rare disease, concerns about confidential breaches
Ran from Jan 2022 to primary completion in Oct 2025, 44 months.
How these figures are worked out, and which studies are left out of them.
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
This study is completed, as verified in Aug 2026. You cannot join it, but the record below documents what was studied.
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Université Paris-Saclay