Triple X Syndrome
Trisomy X is a disorder that affects females and is
characterized by the presence of an additional X
Triple X Syndrome is also known as:
47, XXX
47, XXX karyotype
47, XXX syndrome
Trisomy X syndrome
Triplo X
What is Triple X Syndrome?
Normally, females have two X
 however, females with trisomy
X carry three X chromosomes
in the nuclei of body cells.
 There are specific physical
features (phenotype)
associated with this
chromosomal disorder.
Tall Stature
Skin folds that descend and
cover the inner corners of the
Wide spacing between the eyes
Decreased muscle tone
Curved fifth ("pinky") fingers
Small head circumference
Lower average birth weight
Learning disabilities, such as
delayed speech and language
development, and difficulty
Delayed motor skills, such as
sitting and walking
Problems processing sound
Behavioral and emotional
problems, including attention
deficit hyperactivity disorder
(ADHD), anxiety, and depression
Premature ovarian failure or
ovary malformations (though
infertility is rare)
Menstrual irregularities
Constipation or abdominal pains
Flat feet
Mild concavity of the breastbone
Increased distance
between the eyes in
9 year old girl with
trisomy x
The type of finger
frequently seen in
triple x syndrome
Epicanthal folds and increased
distance between the eyes in 2year old girl with trisomy
Seizures or kidney abnormalities (such as having a single
kidney, or a malformed one), are possible in triple X but
rare — they show up in about 10 percent of cases.
usually of normal intelligence, but IQ scores, especially
verbal scores, tend to be 10 to 15 points below that of
siblings or those in control groups especially if learning
disabilities are not addressed early.
Heart abnormalities have been noted in some isolated
In most cases, either the
mother's egg cell or the
father's sperm cell divides
incorrectly, resulting in an
extra X chromosome in the
child. This random error is
called nondisjunction, and
all the cells in the child's
body will have the extra X
- Occasionally, the extra chromosome results from an
incorrect cell division caused by a random event early in the
embryo's development. If this is the case, the child has a
mosaic form of triple X syndrome, and only some cells have the
extra X chromosome.
- Females with the mosaic form may have less obvious
General Info
This condition occurs in about 1 in
1,000 newborn girls. Five to 10 girls
with triple X syndrome are born in
the United States each day.
Triple X syndrome can be diagnosed
prenatally, through CVS (chorionic
villus sampling, in which tissue
samples are taken from the
placenta) or through amniocentesis.
The condition can also be diagnosed through a postbirth blood test if developmental delays, poor muscle
tone, or other physical characteristics associated with
triple X prompt a doctor to suspect it.
There is no cure for triple X syndrome, but treatments
can help with specific symptoms.
Treatments can include:
Regular doctor visits: At periodic visits, a doctor can monitor a
girl's development for delays, social and language disabilities, or
health problems and treat these promptly.
Additional Info
Trisomy X is not inherited. It is caused by errors during the
normal division of reproductive cells in one of the
In some affected females, only a certain percentage of
their cells may have three X chromosomes, while other
cells have a normal chromosomal make-up (46,XX/47,XXX
These females may have milder symptoms and fewer
developmental and learning problems.
Researchers believe that the symptoms and physical features
associated with trisomy X develop because of overexpression of
the genes that escape normal X-inactivation.
Similar abnormalities include:
Tetra X syndrome, a rare chromosomal abnormality in which
females have two extra X chromosomes in the nuclei of body
cells (48,XXXX karyotype)
Penta X syndrome, an abnormality of the same kind in which
females have three extra X chromosomes in the nuclei of body
cells (49,XXXXX karyotype)
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