Genetic Disorders
Klinefelter Syndrome
클라인펠터증후군
47,XXY karyotype causing male hypogonadism
- How common
- 1 in 600 male births
- Typical age
- Often diagnosed post-puberty
What is it?
Extra X chromosome (47,XXY) → X gene overdose + seminiferous tubule atrophy → low testosterone.
Commonly affected: Testes, brain, skeleton, metabolism
How it develops
- X nondisjunctionMeiotic nondisjunction yields extra X
- SHOX overdose + X-escapeTall stature, KS phenotype
- Tubular hyalinizationTubules destroyed at puberty
- Hypogonadism + infertilityLow testosterone, azoospermia
Symptoms
- InfertilityAzoospermia (>95%)
- Small firm testesSmall (<6 mL), firm testes
- Tall stature, long limbsHeight >+1 SD
- Gynecomastia50% bilateral
- Learning/language difficultyAverage IQ but verbal delays
How it is examined
- Physical examBody habitus + testicular volume (Prader)
- HormonesLow T, high LH/FSH (primary hypogonadism)
- Karyotype (confirmatory)Confirm 47,XXY
Imaging
Mainly clinical/lab diagnosis. DXA for bone density.
- Low bone density
Breast US if evaluating gynecomastia.
- Glandular breast tissue
Non-surgical care
- Testosterone replacementPuberty induction + adult replacement
- Speech/learning therapyEarly speech therapy + learning support
- Metabolic monitoringMonitor for metabolic syndrome, DM, VTE
- Psychosocial supportDepression + self-esteem support
Conservative options are generally tried first. Medications listed here can have side effects — discuss them with your prescriber.
When surgery is considered
Gynecomastia (cosmetic)
Procedures that may be discussed
- Mastectomy
- TESE for assisted reproduction
Outlook
Normal life expectancy. 20× breast cancer risk; HRT prevents osteoporosis.