Klinefelter's syndrome is a relatively common genetic disease
affecting about 1 out of 500 males. Typically an affected male
will look and behave normally from infancy through childhood.
Diagnosis is rarely made before puberty, at which time symptoms
such as small size and firmness of testes, lack of sperm
production, little or no body hair, and breast development become
apparent. Mental retardation often occurs. Men with this
disorder are likely to be very tall and may develop obesity,
osteoporosis, or psychosis.
The disease is caused by an extra X, or female, sex chromosome
in the body cells. Normally, a male has one X chromosome and one
Y chromosome, the latter determining maleness. Body cells in
patients with Klinefelter's syndrome have one or more extra X
chromosomes along with the Y. The extra X chromosomes interfere
with the development of male characteristics. Generally, as the
number of X chromosomes increases, the severity of mental
retardation and malformation also increases. Treatment involves
administering male hormones, which produce more masculine physical
traits, although sterility can never be reversed.