Klinefelter Syndrome Info

Klinefelter’s syndrome, 47,XXY or XXY syndrome is a condition caused by a chromosome aneuploidy. Affected individuals have at least two X chromosomes and at least one Y chromosome. The extra X chromosome is retained because of a nondisjunction event during meiosis (sex cell division).


The XXY chromosome arrangement is one of the most common genetic variations from the XY karyotype, occurring in about 1 in 500 live male births.


  • In adults, possible characteristics vary widely and include little or no indicatinon of affectedness, a lanky, youthful build and facial appearance, or a rounded body type with some degree of gynecomastia (increased breast tissue).
  • Mean I.Q. between 85-90
  1. Affected males are almost always effectively sterile
  2. Some degree of language learning impairment may be present
  3. Hypogonadism, patients will often have a low serum testosterone level but high serum follicle-stimulating hormone (FSH) and luteinizing hormone (LH) levels.
  4. Microorchidism (i.e. small testicles)
  5. Increased risk of germ cell tumors, breast cancer, and osteoporosis

Clinical Management
Although genetic variation is irreversible, symptoms associated with Klinefelter syndrome can be altered or treated in a number of ways, including the use of testosterone treatment