Klinefelter Syndrome
Klinefelter Syndrome (KS), also known as 47,XXY syndrome, is a chromosomal condition where a male has an extra X chromosome. This anomaly was identified in the 1940s by American endocrinologist Harry Klinefelter. KS is one of the most common chromosomal disorders, occurring in approximately 1 in 500 to 1,000 live male births.
Cause
Klinefelter syndrome is not inherited but occurs due to nondisjunction during gametogenesis. This results in an egg or sperm with an extra X chromosome. The risk factor associated with KS is the older age of the mother. The extra chromosome can come from either parent equally.
Signs and Symptoms
Physical Manifestations
Symptoms of KS are often variable, ranging from subtle to more pronounced. Primary features include infertility and small, poorly functioning testicles. Other symptoms may include above-average height, weaker muscles, poor coordination, less body hair, breast growth (gynecomastia), and low libido. These symptoms are often noticed at puberty.
In infants and children, signs may include lower muscle tone, reduced strength, delayed milestones such as sitting up and walking, and less muscle control. Adolescents may exhibit less facial and body hair, broader hips, and weaker bones.
Cognitive Development and Psychological Characteristics
Language learning and reading impairments are common, alongside deficits in executive functions. Around 10% of individuals with KS are autistic. They may also exhibit behavioural differences like higher levels of anxiety, depression, mood dysregulation, and impaired social skills. Some studies suggest that these neurocognitive disabilities are due to the presence of the extra X chromosome.
Diagnosis
Klinefelter Syndrome is diagnosed through genetic testing known as karyotyping. Physical characteristics such as tall stature, low body hair, and small testicles can prompt further investigation. Blood tests showing low testosterone levels with high levels of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) can also indicate KS. In some cases, a spermiogram revealing azoospermia or oligospermia can be part of the diagnosis.
Treatment
Since the genetic variation is irreversible, treatment focuses on managing symptoms. Hormone-replacement therapy with testosterone can address the existing deficiency from puberty onward. This therapy is available in the form of syringes, patches, or gels. Gynecomastia may be treated surgically if necessary.
Behavioural therapy can help mitigate language disorders, school difficulties, and socialisation issues. Occupational therapy is particularly useful for children with dyspraxia.
Infertility Treatment
Methods of reproductive medicine, such as intracytoplasmic sperm injection (ICSI) with testicular sperm extraction (TESE), have enabled men with KS to produce biological offspring.
Pathogenesis
Hypogonadism in KS is characterised by decreased testicular hormone/endocrine function rather than just small testicles. Destruction and hyalinisation of the seminiferous tubules lead to decreased production of FSH and testosterone, impairing spermatogenesis and further endocrine function.
Self-assessment MCQs (single best answer)
Which of the following best describes Klinefelter Syndrome (KS)?
Who identified Klinefelter Syndrome?
The primary cause of Klinefelter Syndrome is:
Which of the following is a common physical manifestation of Klinefelter Syndrome?
At what stage of life are symptoms of Klinefelter Syndrome often noticed?
Which hormone levels are typically elevated in individuals with Klinefelter Syndrome?
What is the primary method used to diagnose Klinefelter Syndrome?
Which therapy is often employed to manage the symptoms of Klinefelter Syndrome?
What is a common cognitive or psychological characteristic associated with Klinefelter Syndrome?
How can infertility in men with Klinefelter Syndrome be addressed?
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