Klinefelter syndrome (KS) is a chromosomal anomaly, which in most cases is characterized by 47 chromosomes instead of the usual 46.
The estimated incidence is 0.15-0.2% of live births.
- the testes are normal prior to puberty and small in post pubertal testes; there is absent spermatogenesis
- the kidneys can be symmetrically enlarged with small 1-8 mm cysts
- post pubertal gynecomastia
- sparse facial and axillary hair
- tall stature
- narrow shoulders
- broad hips
- normal to moderately reduced Leydig cell function
- increased secretion of follicle-stimulating hormone
- androgen deficiency
- normal to slightly decreased verbal intelligence
- ~80% have 47XXY
- ~10% have mosaic 46XY/47XXY
- ~10% have 48XXYY and other less frequent types
These abnormal divisions occur as sporadic events and are not hereditary.
Treatment and prognosis
- increased incidence of male breast malignancy
- increased incidence of germ cell tumors, particularly in the mediastinum 6.
History and etymology
It is named after Harry Klinefelter who first described the syndrome in 1942.
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