General Information on Tetrasomy X and Pentasomy
Tetrasomy X and
Pentasomy X syndromes are also known by the descriptions 48, XXXX; 49, XXXXX;
48xxxx; 49xxxx; Tetra X, Penta X, XXXX, XXXXX, or Quadruple X.
Our human genes are located on chromosomes, normally 46 chromosomes divided into
23 pairs. The last of the 23 pairs are called the sex chromosome; males have an
X and a Y chromosome, while females have two X chromosomes.
In the case of Tetra X syndrome, females have four X chromosomes instead of two.
Therefore, they have 48 chromosomes (48, XXXX) instead of 46. In the case of
Penta X syndrome, there are five X chromosomes or a total of 49 chromosomes (49,
xxxxx). Tetra/Pentasomy X occurs only in females. There are approximately 60
known females worldwide with this rare condition, although it is believed that
there are probably many more who are undiagnosed. The condition was first
identified in 1961.
Symptoms can be relatively minor or more severe. They can include learning
challenges, social difficulties, congenital heart defects, and various physical
attributes common to many chromosome disorders. A description of the physical
and developmental characteristics follows.
It should be noted that Tetra/Penta X girls have in some cases gone on to
college, enjoy sports, and develop lasting personal relationships. The range of
symptoms and severities can be seen by reading through the guestbook entries on
this page. It is one of the goals of this support group and web page to begin to
document the successes and challenges of Tetra/Penta X girls for the benefit of
families and their physicians world wide. We hope to help facilitate research to
increase the understanding of this rare condition by the medical community and
Physical and Developmental Characteristics:
Following is a very
rough, preliminary summary of the physical and developmental characteristics
associated with the diagnosis of tetrasomy X and pentasomy X in females. This is
in no way meant to represent a comprehensive analysis of all features associated
with these diagnoses. It is important to remember that there is an inherent bias
in the collection of this information. All information thus far has been
gathered from the on-line support group for families of girls diagnosed with
tetra- and pentasomy X. These girls have all been identified medically and/or
developmentally. It is therefore possible that the information summarized
represents the more “severe” end of the clinical spectrum.
Because of the informal circumstances under which this information has been
obtained, it would be inappropriate to use this information in any formal
The information below has been provided by 16 families with tetrasomy X, and
four families with pentasomy X.
40% are described as having conotruncal and valvular cardiac defects
10% reported as having abnormal renal structure
15% reported as having visual difficulties (myopia, coloboma, micropthalmus,
optic nerve hypoplasia)
~20% report possible seizure activity, no documented abnormal brain function or
structure through ECG or MRI
Mild developmental delay reported in >90%, low normal functioning reported in 1
young girl, the remaining children are too young to be assessed
· FFT; failure to thrive
· Hypotonic; low muscle tone (occasional constipation has been reported,
possibly related to the hypotonia)
· The majority of girls are reported as being longer and taller, though
hypochondrodysplasia (short stature) has been reported in one young girl
· ~50% of the group members (who are of appropriate age) have experienced normal
menarche, ~50 % have had either abnormal bleeding or amennhorea. The literature
reports 3 women with tetra-X having 4 pregnancies (1 healthy child &1 w/ trisomy
21, 1 stillborn child with omphalocele, and 1 healthy 46,XX female).
· Joint laxity (hips) is reported in ~10 % of the girls in this group and joint
limitations are reported in ~20 %, 2 children are reported as having “clubfoot”,
and 2 others with “crooked great toes”.
· Facial features include; epicanthal folds, flat nasal bridge, upslanting
palpebral fissures(eyes), midface hypoplasia (flattened facial appearance)
· Oral/dental; small mouth, small teeth, failure to develop adult teeth,
“floppy” epiglottus (each reported once).
· Dermatoglyphics; clinodactyly (curved) 5th finger, single palmar creases.
Linear epidermal nevi and skin tabs each reported once.
· Walking; range from 16 months- 4.5 years
· Speech; variable
· “Rule of thumb”: 10-15 pt decrease from parental IQ per supernumerary (extra)
· As stated above, developmental delay tends to be mild, with speech delay more
pronounced than motor delay.
· 2/20 girls in this group have experienced psychiatric symptoms which are well
controlled with medications. These symptoms developed at approximately 15 years
of age in both girls. In general, 2-3% of all individuals with chromosomal
anomalies will experience psychiatric symptoms (“dually diagnosed”). These
symptoms are believed to be related to the chromosomal anomaly.
· Majority of girls are described as pleasant, affectionate, shy, with a good
sense of humor. Emotional lability tends to coincide with frustrations
Please remember that this is simply a list of physical and developmental
features of which the parent and physician of girls with tetra/pentasomy X
should be aware. Speech, Occupational, and Physical Therapy are important
aspects in the care of these young girls. The age of diagnosis, implementation
of early interventions, and physical complications could all effect the long
term prognosis for these children.
This information is meant to be shared amongst families and their daughters’
To join the Tetra X/Penta
X Support Group, send a blank email to:
tetra-Xfirstname.lastname@example.org (case sensitive)
or contact our World
Please email the web host,
comments, or suggestions for this page. Thank you!
Please share your
family's experience with us by signing the guestbook. Include your email address
(and web page if you have one) so that others can contact you.
The contents of this web site are not medical, legal,
technical or therapeutic advice. The information
contained herein is not intended to substitute for
informed professional diagnosis, advice or therapy.
Visitors should not use this information to diagnose or
treat 4X & 5X Syndrome or related disorders without
also consulting a qualified medical or educational
© 2002 Tom Stevenson