Klinefelter Syndrome
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Questions and Answers

What is the approximate prevalence of Klinefelter syndrome in the US population?

  • 1:1000
  • 1:650 (correct)
  • 1:500
  • 1:800
  • What is the primary cause of Klinefelter syndrome?

  • Testicular dysgenesis
  • Nondisjunction of sex chromosomes during meiosis (correct)
  • Advanced maternal age
  • Mitral valve prolapse
  • What is the typical karyotype of an individual with Klinefelter syndrome?

  • 48,XXYY
  • 45,X
  • 46,XY
  • 47,XXY (correct)
  • What is the result of testicular dysgenesis in Klinefelter syndrome?

    <p>Hypogonadism</p> Signup and view all the answers

    What is the typical growth pattern seen in individuals with Klinefelter syndrome?

    <p>Eunuchoid growth pattern</p> Signup and view all the answers

    What is the primary reason for reduced fertility in Klinefelter syndrome?

    <p>Azoospermia</p> Signup and view all the answers

    What is the primary hormone affected in Klinefelter syndrome?

    <p>Testosterone</p> Signup and view all the answers

    What is the typical cognitive feature of Klinefelter syndrome?

    <p>Neurocognitive dysfunction</p> Signup and view all the answers

    What is the confirmatory diagnostic test for Klinefelter syndrome?

    <p>Karyotyping</p> Signup and view all the answers

    What is the primary treatment for Klinefelter syndrome?

    <p>Testosterone substitution</p> Signup and view all the answers

    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.

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