Klinefelter Syndrome (47, XXY)MOSAI-XXNCT07885163
Clinical, Biochemical, and Cytogenetic Heterogeneity in Mosaic 46,XX/47,XXY Sex Chromosome Aneuploidy
An observational study of Klinefelter Syndrome (47, XXY) and Sex Chromosome Aneuploidy, run by Université Paris-Saclay at 1 site in France.
Trial summary
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… Read more about this study
- Who is it for?
- Any age, men only
- Conditions the study is for
- Klinefelter Syndrome (47, XXY), Sex Chromosome Aneuploidy, Disorders of Sex Development (DSD)
- How many people
- 257 participants
- Where
- 1 siteFrance
- Study dates
- 15 Jan 2022to 10 Jan 2026
- Phase
- Observational
- Are there results?
- None posted in the registry
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages Any age
- Men only
- No healthy volunteers
- Child, Adult, Older adult
Study population: patients with a diagnosis of 46,XX/47,XXY mosaicism (mKS-XX) confirmed by cytogenetic assessments
Who may be able to join
- Group A (mKS-XX):
- Minor or adult patients with a diagnosis of 46,XX/47,XXY mosaicism (mKS-XX) confirmed by two cytogenetic assessments (two karyotypes, or one karyotype plus one FISH analysis);
- Followed at Bicêtre Hospital (AP-HP, Université Paris-Saclay) in the Department of Endocrinology and Reproductive Diseases and/or the Department of Pediatric Endocrinology and Diabetology;
- Follow-up period: 2002 to 2023.
- Group B (non-mosaic KS):
- Adult patients with non-mosaic Klinefelter syndrome (47,XXY) confirmed by two cytogenetic assessments (two karyotypes, or one karyotype plus one FISH analysis);
- Followed at Bicêtre Hospital (AP-HP, Université Paris-Saclay) in the Department of Endocrinology and Reproductive Diseases;
- Follow-up period: 2002 to 2023
Who cannot join
- Patients who object to the use of their healthcare data for research (opt-out).
- Patients whose medical records contain insufficient, highly fragmented, or unavailable information, preventing reliable data extraction.
Trial locations and contacts
1 site in 1 country.
France1 site
Bicêtre Hospital (AP-HP), Department of Endocrinology and Reproductive Diseases
Le Kremlin-Bicêtre, 94043
About this study
Official title: Clinical, Biochemical and Cytogenetical Heterogeneity in Individuals With Mosaic 46,XX/47,XXY Sex Chromosome Aneuploidy: Results From the MOSAI-XX Multicenter Study
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.
- Conditions
- Klinefelter Syndrome (47, XXY), Sex Chromosome Aneuploidy, Disorders of Sex Development (DSD), Sex Chromosome Disorders
- Keywords
- 46,XX/47,XXY, Klinefelter syndrome, Sex chromosome aneuploidy, Disorders of sex development, Ovotesticular DSD, Gonadal mosaicism
- Medical subject headings
- Klinefelter Syndrome, Disorders of Sex Development, Sex Chromosome Disorders, Ovotesticular Disorders of Sex Development
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
| Study group | Role | What they receive |
|---|---|---|
| Individuals with 46,XX/47,XXY mosaic formula | 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 | Individuals with homogeneous 47,XXY mosaic formula Collection of clinical, demographic, anthropometric, socio-professional, hormonal and cytogenetic parameters characteristics whenever available |
What is being measured
The primary outcome is the main question the study is designed to answer.
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
Measured: Baseline
Secondary outcomes (11)
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
Measured: 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.
Measured: 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.
Measured: 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.
Measured: 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.
Measured: 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.
Measured: 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.
Measured: 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.
Measured: 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.
Measured: 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.
Measured: 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.
Measured: Baseline
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted21 Oct 2026
- Study start15 Jan 2022
- Primary completion1 Oct 2025
- Study completion10 Jan 2026
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Klinefelter Syndrome (47, XXY)Studies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Observational
- Observational model
- Case-control
- Time perspective
- Retrospective
- Enrolment
- 257 participants (actual)
Sponsor and investigators
- Lead sponsor
- Université Paris-Saclay
- Sponsor type
- University, hospital or other
- Responsible party
- Principal investigator, Maione Luigi, Université Paris-Saclay
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07885163
- Sponsor's protocol ID
- Inserm CEEI/IRB 23-134
- Acronym
- MOSAI-XX
- Status last verified
- Aug 2026
- First submitted
- 3 Feb 2026
- Last updated
- 21 Oct 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- Undecided: Delicate findings, very rare disease, concerns about confidential breaches
Study at a glance
From the registry record, last updated by the sponsor on 21 Oct 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Clinical, Biochemical and Cytogenetical Heterogeneity in Individuals With Mosaic 46,XX/47,XXY Sex Chromosome Aneuploidy: Results From the MOSAI-XX Multicenter Study
- ClinicalTrials.gov ID
- NCT07885163
- Acronym / sponsor ID
- MOSAI-XX / Inserm CEEI/IRB 23-134
- Conditions
- Klinefelter Syndrome (47, XXY), Sex Chromosome Aneuploidy, Disorders of Sex Development (DSD), Sex Chromosome Disorders
- Keywords
- 46,XX/47,XXY, Klinefelter syndrome, Sex chromosome aneuploidy, Disorders of sex development, Ovotesticular DSD, Gonadal mosaicism
- Study type
- Observational
- Recruitment status
- Completed
- Enrolment
- 257 participants (actual)
- Lead sponsor
- Université Paris-SaclayUniversity, hospital or other
- Study start
- 15 Jan 2022 (actual)
- Primary completion
- 1 Oct 2025 (actual)
- Study completion
- 10 Jan 2026 (actual)
- First posted
- 21 Oct 2026 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
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.
Study design
- Observational model
- Case-control
- Time perspective
- Retrospective
- Number of arms
- 2
| Arm | Type | Receives |
|---|---|---|
| Individuals with 46,XX/47,XXY mosaic formula | – | –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 | – | –Individuals with homogeneous 47,XXY mosaic formula Collection of clinical, demographic, anthropometric, socio-professional, hormonal and cytogenetic parameters characteristics whenever available |
Who may qualify
- Sex
- Male only
- Healthy volunteers
- Not accepted
- Age groups
- Child, Adult, Older adult
- Study population
- patients with a diagnosis of 46,XX/47,XXY mosaicism (mKS-XX) confirmed by cytogenetic assessments
Key inclusion criteria (8 listed)
- Minor or adult patients with a diagnosis of 46,XX/47,XXY mosaicism (mKS-XX) confirmed by two cytogenetic assessments (two karyotypes, or one karyotype plus one FISH analysis);
- Followed at Bicêtre Hospital (AP-HP, Université Paris-Saclay) in the Department of Endocrinology and Reproductive Diseases and/or the Department of Pediatric Endocrinology and Diabetology;
- Follow-up period: 2002 to 2023.
- Adult patients with non-mosaic Klinefelter syndrome (47,XXY) confirmed by two cytogenetic assessments (two karyotypes, or one karyotype plus one FISH analysis);
- Followed at Bicêtre Hospital (AP-HP, Université Paris-Saclay) in the Department of Endocrinology and Reproductive Diseases;
Key exclusion criteria (2 listed)
- Patients who object to the use of their healthcare data for research (opt-out).
- Patients whose medical records contain insufficient, highly fragmented, or unavailable information, preventing reliable data extraction.
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Primary outcome
Distribution of primary gonadal phenotype in patients with 46,XX/47,XXY mosaicism
Time frame: Baseline
number and percentage of participants according to primary gonadal phenotype: * bilateral testicles * unilateral testicles * unilateral ovary * unilateral or bilateral ovotestis
11 secondary outcomes
Correlation between XX cell-line percentage and final height within the mKS-XX cohort
Time frame: Baseline
Between-group difference in adult height (mKS-XX vs non-mosaic KS)
Time frame: Baseline
Between-group difference in body mass index (mKS-XX vs non-mosaic KS)
Time frame: Baseline
Between-group difference in gonadal phenotype (mKS-XX vs non-mosaic KS)
Time frame: Baseline
Between-group difference in testicular volume (mKS-XX vs non-mosaic KS)
Time frame: Baseline
Between-group difference in LH levels (mKS-XX vs non-mosaic KS)
Time frame: Baseline
Between-group difference in FSH levels (mKS-XX vs non-mosaic KS)
Time frame: Baseline
Between-group difference in testosterone levels (mKS-XX vs non-mosaic KS)
Time frame: Baseline
Between-group difference in educational level (mKS-XX vs non-mosaic KS)
Time frame: Baseline
Correlation between XX cell-line percentage and delta height within the mKS-XX cohort
Time frame: Baseline
Correlation between XX cell-line percentage and educational level within the mKS-XX cohort
Time frame: Baseline
Results and safety
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 21 Oct 2026.
- Individual participant dataSharing planned: Undecided. Delicate findings, very rare disease, concerns about confidential breaches
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
The record lists no contact. Use the official record to reach the sponsor.
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
An observational study of Klinefelter Syndrome (47, XXY) and Sex Chromosome Aneuploidy, run by Université Paris-Saclay at 1 site in France.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 8 inclusion and 2 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: finished, as of the sponsor's last update on 21 Oct 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in France. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Distribution of primary gonadal phenotype in patients with 46,XX/47,XXY mosaicism (time frame: Baseline). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 21 Oct 2026.