Cytogenetic disorders involving sex
It is best defined as male hypogonadism that occurs
when there are two or more X chromosomes and at
least one Y chromosome .
This complement results from nondisjunction during
the meiotic division in one of the parents .
Clinical features include:-Patient is tall (mostly for the lower
-Lack of secondary sexual
characteristics as deep voice , beard and
male distribution of pubic hair .
- Small atrophic testes and small penis
-I.Q may be lower than normal
Patients with Klinefelter syndrome have a higher risk
for breast cancer (20 times more common than in
It can rarely diagnosed before puberty because
testicular abnormality does not develop before early
The serum testosterone levels are
lower than normal, and serum
gonadotropin(FSH,LH) levels and
estradiol levels are elevated.
Sperm count is zero .
Small atrophic testes and small penis
1-The testicular tubules are totally atrophied
and replaced by pink hyaline collagenous
Klinefelter syndrome is the most common
causes of male hypogonadism ,reduced
spermatogenesis and male infertility.
2- barr body(darkly staining small mass in
contact with the nuclear membrane of
interphase nucleus )
Barr bodyies are present in all somatic
cells of normal females, e.g in smears of
buccal squamous epithelial cells .
-Most of cases (90%) associated with
result from Non-disjunction
during meiotic division in one of parents .
Approximately 10% of patients show
mosaic patterns, including :