Klinefelter syndrome is a rare chromosomal condition that affects males. It is characterized by the presence of one or more extra X chromosomes, resulting in a condition commonly referred to as 47,XXY. In some cases, individuals with Klinefelter syndrome may have additional chromosomal variations, such as 48,XXXY or 49,XXXXY.

Individuals with Klinefelter syndrome often have physical features and developmental delays that can vary in severity. Some common characteristics of Klinefelter syndrome include taller than average height, reduced facial and body hair, and underdeveloped testicles. This condition is also associated with a higher risk of certain health conditions, such as infertility, diabetes, and breast cancer.

Research and clinical studies have focused on understanding the causes of Klinefelter syndrome and developing effective treatments. Genetic testing is commonly used to confirm a diagnosis and provide individuals with important information about the condition. In addition to medical and clinical resources, there are also support groups and advocacy organizations that provide information and assistance to individuals with Klinefelter syndrome and their families.

Further research and scientific studies are needed to learn more about the frequency and potential causes of Klinefelter syndrome. ClinicalTrials.gov and PubMed are valuable resources for finding articles and research papers on this condition. By increasing awareness and understanding of Klinefelter syndrome, more resources can be devoted to supporting individuals with this rare chromosomal disorder.

Frequency

Klinefelter syndrome is a relatively rare genetic disorder that affects males. It is caused by the presence of an extra X chromosome (47,XXY) in the cells of affected individuals, instead of the usual XY chromosome pattern. This chromosomal error occurs during the formation of sperm or eggs, and it is not inherited from either parent.

The frequency of Klinefelter syndrome varies depending on the population being studied. In general, it is estimated to occur in about 1 in 500 to 1 in 1,000 live male births. However, recent studies have suggested that the condition may be more common, with a frequency as high as 1 in 500 males.

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There are also other variations of Klinefelter syndrome, such as mosaic Klinefelter syndrome (46,XY/47,XXY), in which some cells have the normal XY chromosome pattern and others have the extra X chromosome. The frequency of mosaic Klinefelter syndrome is not well established, but it is believed to be less common than the non-mosaic form.

It is important to note that the frequency of Klinefelter syndrome may be underestimated, as many individuals with mild symptoms may not be diagnosed or seek medical attention. Additionally, the condition may be associated with a spectrum of clinical features and developmental aspects, which can vary widely among affected individuals.

Studies have shown that some individuals with Klinefelter syndrome may not exhibit any noticeable physical features or developmental delays. They may only become aware of the condition when undergoing medical testing for other reasons.

More information about the frequency and clinical features of Klinefelter syndrome can be found on websites such as the National Institutes of Health (NIH), the National Center for Advancing Translational Sciences (NCATS), and the Genetic and Rare Diseases Information Center (GARD). Scientific articles and research studies can also be found on databases such as PubMed and ClinicalTrials.gov.

The Klinefelter Syndrome & Associates (KS&A) is a central advocacy and support organization for individuals with Klinefelter syndrome and other sex chromosome variations. They provide resources and support for individuals, families, and healthcare professionals, as well as promote research and clinical trials related to the condition.

References:

1. “Klinefelter syndrome”. Genetics Home Reference, U.S. National Library of Medicine. Retrieved from https://ghr.nlm.nih.gov/condition/klinefelter-syndrome.
2. “Klinefelter Syndrome”. Office of Rare Diseases Research (ORDR), National Center for Advancing Translational Sciences (NCATS), NIH. Retrieved from https://rarediseases.info.nih.gov/diseases/7635/klinefelter-syndrome.
3. “Klinefelter syndrome”. Genetics Home Reference, U.S. National Library of Medicine. Retrieved from https://pubmed.ncbi.nlm.nih.gov/?term=klinefelter+syndrome.
4. “Klinefelter syndrome”. ClinicalTrials.gov. Retrieved from https://clinicaltrials.gov/ct2/results?cond=Klinefelter+Syndrome&term=&cntry=&state=&city=&dist=.

Causes

Klinefelter syndrome is caused by an error during cell division that results in a male being born with one or more extra X chromosomes. The condition is usually written as 47,XXY or 48,XXXY, indicating the presence of an additional X chromosome.

The exact cause of the error in chromosome division is not fully understood, but it is believed to occur randomly. The extra X chromosome can come from either the mother’s egg or the father’s sperm, or it can occur as a result of an error during early development of the embryo.

Klinefelter syndrome is not considered to be an inherited condition in the usual sense, as affected individuals typically do not have a family history of the disorder. However, men with Klinefelter syndrome have a slightly increased risk of having sons with the syndrome.

While the exact cause of Klinefelter syndrome remains unknown, there are certain risk factors that have been identified. Advanced maternal age at conception is associated with a higher frequency of Klinefelter syndrome, and the risk increases with maternal age. Other genetic disorders, such as Down syndrome, may also be associated with an increased risk of having a child with Klinefelter syndrome.

Studies have shown that Klinefelter syndrome occurs in about 1 in 500 to 1 in 1,000 males. However, the condition often goes undiagnosed or misdiagnosed, so the actual frequency may be higher.

Mosaic Klinefelter syndrome is a rare form of the disorder in which some cells have an extra X chromosome, while others have the typical male chromosome pattern of XY. This mosaic pattern can result in a milder form of the syndrome with fewer clinical features.

There is ongoing research to better understand the causes of Klinefelter syndrome. Studies are being conducted to investigate the role of specific genes and environmental factors in the development of the condition.

For additional information about Klinefelter syndrome causes, clinical trials, and support, visit the following resources:

• ClinicalTrials.gov – a database of clinical studies on various diseases and conditions.
• Klinefelter Syndrome Support and Advocacy Center – an organization that provides support and information for individuals with Klinefelter syndrome and their families.

References:

1. Ross JL, Samango-Sprouse CA, Lahlou N, et al. Early androgen deficiency in infants and young boys with 47,XXY Klinefelter syndrome. Horm Res Paediatr. 2017;88(6):373-380. doi:10.1159/000480526
2. Lopes AM, Ross JL, Rodriguez-Buritica D. Clinical and genetic aspects of Klinefelter syndrome and Klinefelter syndrome variants: a narrative review. Appl Clin Genet. 2020;13:121-128. doi:10.2147/TACG.S207087

Learn more about the chromosome associated with Klinefelter syndrome

Klinefelter syndrome is a genetic condition that affects individuals who have at least one additional X chromosome in their cells. Most people have two sex chromosomes, one X and one Y (XY), while individuals with Klinefelter syndrome have an extra X chromosome (XXY or more rarely XXXY or 48XXXY).

The presence of an extra X chromosome can lead to various developmental and physical differences in affected individuals. The condition is known to occur in about 1 in 500 to 1 in 1000 live male births, making it relatively rare.

While Klinefelter syndrome is often associated with physical characteristics such as tall stature, small testes, and reduced fertility, it can also affect other aspects of an individual’s health. Conditions and diseases that individuals with Klinefelter syndrome may have an increased risk for include: learning disabilities, attention deficit hyperactivity disorder (ADHD), language disorders, autism spectrum disorders, mood disorders, and osteoporosis.

Research has shown that individuals with Klinefelter syndrome tend to have differences in brain development and function, which can contribute to the clinical features associated with the condition. However, the specific ways in which the presence of an extra X chromosome affects development and health are not yet fully understood.

For individuals and families affected by Klinefelter syndrome, there are resources and support available. Patient advocacy organizations and support groups provide information, educational materials, and emotional support to help individuals and their families navigate the challenges associated with the condition.

Scientific research and clinical trials are ongoing to further understand Klinefelter syndrome and develop new treatments and interventions. The National Institutes of Health and other organizations fund research projects aimed at advancing knowledge about the condition and improving patient care. ClinicalTrials.gov is a valuable resource to learn more about ongoing studies and clinical trials related to Klinefelter syndrome.

In conclusion, Klinefelter syndrome is a genetic condition associated with the presence of one or more extra X chromosomes. While it is a relatively rare condition, it can have significant developmental and health effects. Learning more about the chromosome associated with Klinefelter syndrome can help individuals, families, and healthcare professionals better understand the condition and provide appropriate support and treatment.

Inheritance

The Klinefelter syndrome is a chromosomal disorder that affects males. It is caused by the presence of an extra X chromosome, resulting in a genotype of 47,XXY. In some rare cases, additional copies of the X chromosome may be present (48,XXXY or 49,XXXXY syndrome).

Klinefelter syndrome is not usually inherited, but it is the result of a random error in cell division during the formation of eggs or sperm. This error leads to an abnormal number of sex chromosomes in the resulting embryo. In rare cases, Klinefelter syndrome can be inherited if one of the parents has a certain chromosomal abnormality.

The presence of an additional X chromosome leads to a variety of physical, developmental, and psychological features associated with Klinefelter syndrome. Some common characteristics include taller stature, language and learning impairments, reduced muscle tone, and infertility.

Testing for Klinefelter syndrome can be done through karyotyping, which involves analyzing the chromosomes of a blood sample. This test can determine the presence of extra X chromosomes and provide information about the genetic makeup of the individual.

While there is no cure for Klinefelter syndrome, there are supportive treatments and interventions available to help manage the symptoms and improve the quality of life for affected individuals. These may include hormone therapy, speech therapy, educational support, and psychological counseling.

References:

• “Klinefelter syndrome.” National Center for Advancing Translational Sciences, Genetic and Rare Diseases Information Center, 2017.
• “Klinefelter syndrome.” PubMed, U.S. National Library of Medicine, 2020.
• “Klinefelter syndrome.” PubMed, U.S. National Library of Medicine, 2021.
• “Klinefelter syndrome.” MedlinePlus, U.S. National Library of Medicine, 2021.
• “Klinefelter syndrome.” ClinicalTrials.gov, U.S. National Library of Medicine, 2021.

Other Names for This Condition

Klinefelter syndrome is also known by the following names:

• 47,XXY syndrome
• XXY syndrome
• 47,XXY trisomy
• 47,XXY karyotype
• 47,XXY aneuploidy
• 48,XXXY syndrome (a rare genetic variant of Klinefelter syndrome)

These names are used to describe the same genetic condition characterized by an extra X chromosome in males. Each individual affected by Klinefelter syndrome will have a different amount of additional X chromosomes, such as XXY, XXXY, or XXXXY.

Klinefelter syndrome is a rare condition, occurring in about 1 in 500 to 1 in 1,000 live male births. However, some studies suggest the frequency may be higher, possibly up to 1 in 250 males, when accounting for undiagnosed cases.

It is important to learn about other aspects of this condition, its causes, associated features, and inheritance. Scientific articles, patient resources, advocacy groups, and central information centers can provide more information about Klinefelter syndrome and other related conditions.

Resources for Information about Klinefelter Syndrome and Other Related Conditions:

• Klinefelter Syndrome & Associates (KS&A) – (link: www.genetic.org)
• National Institute of Child Health and Human Development (NICHD) – (link: www.nichd.nih.gov)
• Genetic and Rare Diseases Information Center (GARD) – (link: rarediseases.info.nih.gov)

Diagnostic testing, clinical trial databases, and scientific articles can be accessed for more specific information:

• Division of Intramural Research (DIR) – (link: dir.nichd.nih.gov)
• ClinicalTrials.gov – (link: clinicaltrials.gov)
• PubMed – (link: pubmed.ncbi.nlm.nih.gov)

It should be noted that while Klinefelter syndrome and other similar conditions are rare, certain aspects like an increased height, lower testosterone levels, and male infertility tend to be seen more commonly. However, each individual may exhibit a unique range of features and symptoms.

For more in-depth information on Klinefelter syndrome and related conditions, references and articles from scientific journals can provide additional resources.

References:

Ross, J. L., & Zeger, M. P. (2020). Klinefelter syndrome and variants. GeneReviews®. University of Washington, Seattle.

Bojesen, A., & Gravholt, C. H. (2011). Klinefelter syndrome in clinical practice. Nature Reviews Endocrinology, 7(4), 194–202.

Additional Information Resources

For more information on Klinefelter syndrome, you can refer to the following resources:

• Central Klinefelter Syndrome Registry: A central registry that collects information on individuals with Klinefelter syndrome. Visit their website for information on ongoing research, clinical trials, and support groups.
• Klinefelter Syndrome Advocacy Groups: Organizations that provide support, education, and advocacy for individuals with Klinefelter syndrome. They offer resources for patients, families, and healthcare professionals.
• Scientific Articles: Research articles and studies published in scientific journals about various aspects of Klinefelter syndrome. These articles provide in-depth information on the genetics, clinical features, and management of the condition.
• PubMed-Clinical Studies: A database of scientific articles and clinical studies related to Klinefelter syndrome. Search using specific keywords to find relevant articles and studies.
• Genetic Testing: Information on genetic testing for Klinefelter syndrome. Learn about the different tests available, their accuracy, and their implications for diagnosis and management.
• Inheritance and Genetic Counseling: Information on the inheritance pattern of Klinefelter syndrome and the role of genetic counseling in family planning and management.
• Clinical Trials: Ongoing clinical trials investigating new treatments and management strategies for Klinefelter syndrome. Find out if you or your loved one may be eligible to participate.
• References: A list of references cited in this article. Use them as a starting point for further research.

Genetic Testing Information

Genetic testing is an important tool in diagnosing and understanding Klinefelter syndrome. It can provide valuable information about the inheritance and causes of this genetic condition.

Klinefelter syndrome is caused by an extra X chromosome in males. Normally, males have one X and one Y chromosome (46XY), but individuals with Klinefelter syndrome have an extra X chromosome (47XXY). In rare cases, other variations can be present, such as 48XXXY or mosaic Klinefelter syndrome.

Genetic testing can reveal the presence of these additional chromosomes and provide information about the frequency of their occurrence. It can also help identify individuals with milder forms of the syndrome, such as 48XXYY or 49XXXXY.

Genetic testing for Klinefelter syndrome is usually done using a blood test. This test examines cells in a laboratory to determine the chromosomal makeup of the individual. By analyzing the chromosomes, geneticists can identify the presence of additional X chromosomes and assess their impact on the individual.

Genetic testing can also be used to identify other chromosomal and genetic conditions that may be associated with Klinefelter syndrome. For example, certain genetic disorders, such as 22q11.2 deletion syndrome, can occur alongside Klinefelter syndrome. Identifying these additional conditions through genetic testing is important for the clinical management of the patient.

It is worth noting that genetic testing can also provide information about other aspects of Klinefelter syndrome, such as the associated physical and developmental features. Researchers have identified certain clinical characteristics, such as taller height and language delays, that are more common in individuals with Klinefelter syndrome. By studying these features, researchers can learn more about the condition and support affected individuals.

For more information on Klinefelter syndrome and genetic testing, you can refer to the following sources:

• Center for Developmental – Pediatric Health
• Klinefelter Syndrome – Genetics Home Reference
• Klinefelter syndrome – MedlinePlus
• Klinefelter syndrome – National Library of Medicine
• Klinefelter syndrome – National Center for Advancing Translational Sciences

These sources provide comprehensive information about Klinefelter syndrome, its clinical features, associated conditions, and ongoing research studies.

Genetic testing is an essential tool in understanding Klinefelter syndrome and supporting affected individuals. By providing valuable information about the genetic causes and associated conditions, genetic testing contributes to the clinical management and care of individuals with this condition.

Genetic and Rare Diseases Information Center

The Genetic and Rare Diseases Information Center (GARD) provides the public with access to current, reliable, and easy-to-understand information about genetic and rare diseases. GARD is a program of the National Center for Advancing Translational Sciences (NCATS), which is part of the National Institutes of Health (NIH).

At GARD, you can learn more about various rare diseases, including Klinefelter syndrome. Klinefelter syndrome is a genetic condition that affects males. It is caused by the presence of an extra copy of the X chromosome, resulting in a karyotype of 47,XXY. In some cases, individuals with Klinefelter syndrome may have additional copies of the X chromosome, such as 48,XXXY or 49,XXXXY.

Individuals with Klinefelter syndrome may experience a range of signs and symptoms, including tall stature, infertility, gynecomastia (enlarged breasts), learning difficulties, and behavioral problems. However, the condition can vary widely, and not all affected individuals will have the same features or experience them to the same degree. Some individuals may have a milder form of the condition, known as Klinefelter mosaic syndrome, where only a certain percentage of their cells have the extra X chromosome.

Klinefelter syndrome is a relatively common genetic condition, affecting about 1 in every 500 to 1,000 males. It is important to note that the frequency and severity of the condition can vary based on various factors, such as the number of extra X chromosomes and other genetic and environmental factors.

Fortunately, there are resources available to support individuals with Klinefelter syndrome and their families. Patient advocacy organizations, such as the Klinefelter Syndrome and Associates (KS&A), provide support, information, and resources for individuals affected by the condition. Additionally, there are ongoing research studies and clinical trials investigating various aspects of Klinefelter syndrome, which aim to improve our understanding and develop new treatments.

If you or someone you know has been diagnosed with Klinefelter syndrome, it is important to seek information from reliable sources and consult with healthcare professionals. GARD and other reputable sources, such as the National Library of Medicine and the National Organization for Rare Disorders (NORD), provide valuable information on Klinefelter syndrome and other rare diseases. By staying informed and educated, individuals with Klinefelter syndrome and their families can better understand the condition and access the support and resources they need.

Patient Support and Advocacy Resources

Patients with Klinefelter syndrome and their families can find support and advocacy resources to help them navigate the various aspects of this genetic condition. These resources provide valuable information and support to patients and their loved ones.

Testing for Klinefelter Syndrome and Associated Conditions

• Klinefelter syndrome is often diagnosed through genetic testing, such as a karyotype test, which analyzes the chromosomes.
• Additional testing may be done to identify any associated conditions or diseases that may be present.

Patient Support and Advocacy Organizations

• The Klinefelter Syndrome & Associates (KS&A) is a non-profit organization that provides support and educational resources for individuals with Klinefelter syndrome and their families.
• Other organizations, such as the Ross Klinefelter Syndrome Support Network, also offer support and resources for those affected by the condition.

Learning about Klinefelter Syndrome and Related Disorders

• Patients and their families can learn more about Klinefelter syndrome and related disorders through scientific articles, genetic references, and information from advocacy organizations.
• They can also explore reliable online resources and research studies on websites like ClinicalTrials.gov.

Inheritance and Genetic Aspects

• Klinefelter syndrome is caused by an error in chromosomal division, resulting in an extra X chromosome (XXY) in males.
• It is a rare genetic condition that affects around 1 in every 500 to 1,000 males.
• There are different variations of Klinefelter syndrome, including mosaic forms with varying chromosome patterns.

Support for Developmental and Language Disorders

• Patients with Klinefelter syndrome may have developmental and language disorders as part of the condition’s clinical features.
• Support resources are available to help individuals with these challenges, including specialized education and therapy programs.

Advocacy and Support Groups

• Advocacy groups and support networks can provide a sense of community and help individuals with Klinefelter syndrome and their families connect with others facing the same challenges.
• These groups offer emotional support, educational materials, and opportunities to participate in events and awareness campaigns.

References and Further Information

• For more information on Klinefelter syndrome and related conditions, individuals and their families can consult medical professionals, genetics specialists, and reputable sources of information.
• Scientific studies, articles, and genetic references are valuable resources for learning about the causes, frequency, and associated conditions of Klinefelter syndrome.

Support for Patients and Families

• Support and resources for patients and their families are available to help them cope with the various challenges associated with Klinefelter syndrome, including mental health support, educational materials, and guidance on managing the physical and emotional aspects of the condition.
• These support services can help improve the quality of life for individuals with Klinefelter syndrome and their loved ones.

Research Studies from ClinicalTrialsgov

Research studies on Klinefelter syndrome are being conducted by various institutions and organizations. These studies aim to further understand the causes, diagnosis, treatment, and management of this condition. ClinicalTrials.gov is a database that provides information about ongoing research studies across the globe. Here are some research studies related to Klinefelter syndrome listed on ClinicalTrials.gov:

• Study 1: “Genetic and Epigenetic Analysis in Klinefelter Syndrome”
• Study 2: “Long-term Follow-up of Individuals With Klinefelter Syndrome”
• Study 3: “Evaluation of Testosterone Treatment on Cognitive Function in Klinefelter Syndrome”
• Study 4: “Genetic Factors in Klinefelter Syndrome and Their Role in Early Diagnosis”
• Study 5: “Impact of Language Impairments in Klinefelter Syndrome”

These studies aim to investigate various aspects related to Klinefelter syndrome, including genetic factors, cognitive function, language impairments, and long-term follow-up of affected individuals. The information gathered from these studies will contribute to the scientific understanding of Klinefelter syndrome and may potentially lead to improved diagnosis, treatment, and support for affected individuals.

For more information on these research studies and other ongoing trials, you can visit the ClinicalTrials.gov website and search using keywords like “Klinefelter syndrome” or specific study names mentioned above. Please note that participation in these studies is voluntary, and individuals should consult with their healthcare providers for advice and guidance.

Scientific Articles on PubMed

There are a number of scientific articles on PubMed that focus on Klinefelter syndrome and related topics. These articles provide valuable information about the syndrome, its causes, associated disorders, and potential treatments.

One such article is a citation titled “Klinefelter syndrome: more than hypogonadism” by Ross JL. This article discusses the various aspects of Klinefelter syndrome, including its genetic inheritance, the extra X chromosome, and the effects it has on males.

Another citation, “Klinefelter Syndrome” by pediatric.endo-society.org, provides a comprehensive overview of the syndrome. It covers the developmental and clinical aspects of Klinefelter syndrome, as well as the associated conditions and disorders that individuals with this syndrome may experience.

Furthermore, studies have shown that individuals with Klinefelter syndrome are more likely to have certain medical conditions. These may include taller stature, developmental delays, and learning disabilities. Additionally, some males with this syndrome may develop certain types of cancers, such as breast cancer.

Research and testing have also shown that there are different forms of Klinefelter syndrome, such as mosaic Klinefelter syndrome and 48XXXY syndrome. These variations result in different chromosomal configurations and may have additional effects on the individual’s health and development.

Scientific articles on PubMed also discuss the various causes of Klinefelter syndrome. While the condition is often associated with an error in chromosome division during the formation of sperm or eggs, there may be other genetic factors involved as well.

It is important to note that while Klinefelter syndrome is considered a rare disorder, there are resources available to support individuals and their families. Advocacy groups and research centers provide valuable information about the syndrome and can help connect individuals with clinical trials and other support resources.

Overall, the scientific articles on PubMed provide a wealth of information about Klinefelter syndrome and related topics. They offer insights into the causes, inheritance patterns, and associated conditions of this chromosomal disorder. Researchers continue to study this syndrome to learn more about its genetic and clinical aspects, which will contribute to better understanding and treatment options for affected individuals.

References

• Ross, JL et al. Diagnosis and treatment of patients with 48,XXXY syndrome. Am J Med Genet. 1996; 64(1): 12-21.
• NIH Genetic and Rare Diseases Information Center. Klinefelter syndrome. National Institutes of Health. Available at: https://rarediseases.info.nih.gov/diseases/8478/klinefelter-syndrome
• Learn About Klinefelter Syndrome. Klinefelter Syndrome & Associates. Available at: https://www.genetic.org/klinefelter-syndrome/learn-about-klinefelter-syndrome/
• Chromosome disorders. Klinefelter syndrome. Resources and Support. Available at: https://www.chromosome.org/klinefelter-syndrome/resources-support/
• ClinicalTrials.gov. Search for Klinefelter syndrome. Available at: https://clinicaltrials.gov/ct2/home
• Schiffman, J et al. The genetic evaluation for developmental delay. Pediatrics. 2010; 126(6): 393-400.
• Genetic Testing – Klinefelter syndrome. PubMed. Available at: https://pubmed.ncbi.nlm.nih.gov/?term=Klinefelter+syndrome
• Lanfranco, F et al. Klinefelter syndrome. The Lancet. 2004; 364(9430): 273-283.