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What is the approximate prevalence of Klinefelter syndrome in the US population?
What is the primary cause of Klinefelter syndrome?
What is the typical karyotype of an individual with Klinefelter syndrome?
What is the result of testicular dysgenesis in Klinefelter syndrome?
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What is the typical growth pattern seen in individuals with Klinefelter syndrome?
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What is the primary reason for reduced fertility in Klinefelter syndrome?
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What is the primary hormone affected in Klinefelter syndrome?
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What is the typical cognitive feature of Klinefelter syndrome?
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What is the confirmatory diagnostic test for Klinefelter syndrome?
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What is the primary treatment for Klinefelter syndrome?
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Study Notes
Klinefelter Syndrome
- Prevalence: approximately 1:650 in the US population
- One of the most common causes of male hypogonadism
Etiology
- Usually due to nondisjunction of sex chromosomes during meiosis
- Associated with advanced maternal age
Karyotype
- 47,XXY (most common)
- Rarely 48,XXXY or 48,XXYY
- Presence of a Barr body (inactivated X chromosome)
Pathophysiology
- Testicular dysgenesis leads to:
- Seminiferous tubules dysgenesis → loss of Sertoli cells → ↓ inhibin B → ↑ FSH
- Leydig cell dysfunction → ↓ testosterone → ↑ LH
- Both ↑ LH and ↑ FSH lead to increased conversion of testosterone to estrogen
Clinical Features
- Testicular dysgenesis and subsequent testosterone deficiency manifest at the onset of puberty
- Signs and symptoms of hypoandrogenism:
- Eunuchoid growth pattern: tall, slim stature with long extremities
- Gynecomastia
- Reduced facial and body hair
- Testicular atrophy
- Reduced fertility and libido
- Frequent azoospermia
- Micropenis
- Osteoporosis (common feature in adulthood)
- Possible developmental delay
- Neurocognitive dysfunction:
- Impaired executive function and memory
- Decreased intelligence
- Language impairment:
- Affects expression more than comprehension
- Poor social skills
Associated Disorders
- Mitral valve prolapse
- Increased risk of breast and testicular cancer
- Metabolic syndrome
Diagnostics
- Clinical presentation
- Hormone levels:
- ↑ FSH and LH
- ↓ Testosterone with ↑ aromatase and ↑ estrogen levels
- Testicular biopsy (performed after puberty):
- Seminiferous tubules fibrosis
- Leydig cells hyperplasia
- Karyotyping: confirmatory test
Treatment
- Life-long testosterone substitution
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Description
This quiz covers the prevalence, etiology, and pathophysiology of Klinefelter syndrome, a genetic disorder affecting male hypogonadism. Learn about the causes, symptoms, and characteristics of this condition.
