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Klinefelter Syndrome

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  1. Epidemiology
    1. Most common major sexual differentiation abnormality
    2. Incidence of klinefelter syndrome in specific cohorts
      1. Newborn males: 1 in 500 to 1000
      2. Male Breast Cancer: 7.5%
      3. Infertile males: 3%
      4. Mild mental retardation: 1%
  2. Pathophysiology
    1. Results in testicular dysgenesis
    2. Chromosomal abnormality with 47,XXY karyotype
      1. Abnormality of nondisjunction during meiosis
      2. Maternal or paternal origin
      3. Most of additional X Chromosome is inactivated
        1. Functioning extra genes confer phenotype
        2. More severe cases with XXXY, XXXXY or XXYY
        3. Less severe cases with mosaicism (>1 cell line)
  3. Signs
    1. Late Eunuchoid body proportions
      1. Tall, slim and underweight
      2. Long legs and short torso
      3. Obesity and varicosities may occur in 33% of patients
    2. Hypergonadotropic Hypogonadism
      1. Testes small and firm (usually <2.0 cm or 2 ml)
      2. Penis small
      3. Azoospermia or oligospermia (and Infertility)
    3. Other signs of Hypoandrogenism
      1. Gynecomastia (bilateral and painless)
      2. Decreased facial hair, but pubic hair abundant
  4. Labs
    1. Karyotype: XXY
    2. Post-Puberty labs
      1. Follicle Stimulating Hormone (FSH) increased
      2. Leutinizing Hormone (LH) increased
      3. Inhibin B decreased
      4. Increased estradiol to testosterone ratio
  5. Associated Conditions
    1. Mild mental retardation
      1. Motor function delay
      2. Language comprehension problems
      3. Speech may also be affected
    2. Learning Disorders
      1. Attention Deficit Disorder
      2. Dyslexia
    3. Social maladjustment
    4. Mental illness
    5. Thyroid dysfunction
    6. Diabetes Mellitus
    7. Lung disease
    8. Breast Cancer (20x risk of healthy men)
    9. Osteoporosis
  6. Management: General
    1. Complete neurodevelopment evaluation at diagnosis
      1. Indicated if diagnosis in childhood
    2. Breast Cancer surveillance
  7. Management: Testosterone Replacement after age 11
    1. Start
      1. Long acting Testosterone 25-50 mg IM q3-4 weeks
      2. Increase Testosterone dose by 50 mg q6-9 months
      3. Goal: 200 to 250 mg q3-4 weeks
    2. Maintenance
      1. Convert to Testosterone patches when at 200-250 mg
  8. Resources
    1. American Association for Klinefelter Syndrome
      1. http://www.aaksis.org
    2. Klinefelter Syndrome Support Group
      1. http://klinefeltersyndrome.org
  9. References
    1. Mendoki (1991) J Am Acad Child Adolesc Psychiatry :
    2. Schwartz (1991) Endocrinol Metab Clin North Am 20:153
    3. Smyth (1998) Arch Intern Med 158(12):1309
    4. Behrman (2000) Nelson Pediatrics, Saunders, p. 1746-9
    5. Wattendorf (2005) Am Fam Physician 72:2259-62
    6. Wilson (1991) Harrison's Medicine, McGraw-Hill, p. 1800

Klinefelter's Syndrome (C0022735)

Definition (MSH)A form of male HYPOGONADISM, characterized by the presence of an extra X CHROMOSOME, small TESTES, seminiferous tubule dysgenesis, elevated levels of GONADOTROPINS, low serum TESTOSTERONE, underdeveloped secondary sex characteristics, and male infertility (INFERTILITY, MALE). Patients tend to have long legs and a slim, tall stature. GYNECOMASTIA is present in many of the patients. The classic form has the karyotype 47,XXY. Several karyotype variants include 48,XXYY; 48,XXXY; 49,XXXXY, and mosaic patterns ( 46,XY/47,XXY; 47,XXY/48,XXXY, etc.).
Definition (CSP)genetic disease that produces sterile males with small testes lacking sperm due to XXY karyotype.
ConceptsCongenital Abnormality (T019) , Disease or Syndrome (T047)
ICD9758.7, 758.7
MSHD007713
EnglishHypogonadotropic Hypogonadism, KLINEFELTER SYNDROME, Klinefelter Syndromes, Klinefelter's Syndrome, Klinefelter's syndrome karyotype 47 XXY, Klinefelters Syndrome, XXY Klinefelter's syndrome, XXY syndrome, XXY trisomy
Spanishsindrome de Klinefelter, sindrome XXY
Parent ConceptsCongenital chromosomal disease (C0008626), Mental Retardation (C0025362), Syndrome (C0039082), Hypogonadism (C0020619), Sex Differentiation Disorders (C0036875), Sex Chromosome Disorders (C0949683), Endocrine Syndrome (C1333387), Sex Chromosome Aberrations (C0036868), Klinefelter's syndrome - male with more than two X chromosomes (C0432474), Ambiguous concept (C1274012), Duplicate concept (C1274013)
SourcesCOSTAR, CSP, DXP, ICD9CM, LCH, MEDLINEPLUS, MSH, MTH, MTHICD9, NCI, NDFRT, SCTSPA, SNOMEDCT
Derived from the NIH UMLS (Unified Medical Language System)



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