Trisomy 8 causes Warkany syndrome 2, a human
chromosomal disorder caused by having three copies (
trisomy) of
chromosome 8
Chromosome 8 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 8 spans about 145 million base pairs (the building material of DNA) and represents between 4.5 and 5.0% of the total DNA ...
. It can appear with or without
mosaicism.
Characteristics
Complete trisomy 8 causes severe effects on the developing fetus and can be a cause of
miscarriage
Miscarriage, also known in medical terms as a spontaneous abortion and pregnancy loss, is the death of an embryo or fetus before it is able to survive independently. Miscarriage before 6 weeks of gestation is defined by ESHRE as biochemical ...
.
Complete trisomy 8 is usually an early lethal condition, whereas trisomy 8
mosaicism is less severe and individuals with a low proportion of affected cells may exhibit a comparatively mild range of physical abnormalities and developmental delay. Individuals with trisomy 8 mosaicism are more likely to survive into childhood and adulthood, and exhibit a characteristic and recognizable pattern of developmental abnormalities. Common findings include stunted psychomotor development, moderate to severe intellectual disability, variable growth patterns which can result in either abnormally short or tall stature, an expressionless face, and many musculoskeletal, visceral, and eye abnormalities, as well as other
anomalies. A deep plantar furrow is considered to be pathognomonic of this condition, especially when seen in combination with other associated features. The type and severity of symptoms are dependent upon the location and proportion of trisomy 8 cells compared to normal cells.
Other conditions
Trisomy 8 mosaicism affects wide areas of chromosome 8 containing many genes, and can thus be associated with a range of symptoms.
* Mosaic trisomy 8 has been reported in rare cases of
Rothmund–Thomson syndrome, a genetic disorder associated with the
DNA helicase RECQL4 on chromosome 8q24.3. The syndrome is "characterized by
skin atrophy
Atrophoderma refers to conditions involving skin atrophy.
Types include:
* Follicular atrophoderma
* Linear atrophoderma of Moulin
* Atrophoderma of Pasini and Pierini
Morphea is a form of scleroderma that involves isolated patches of hard ...
,
telangiectasia,
hyper- and
hypopigmentation,
congenital skeletal abnormalities
A birth defect, also known as a congenital disorder, is an abnormal condition that is present at birth regardless of its cause. Birth defects may result in disabilities that may be physical, intellectual, or developmental. The disabilities ca ...
, short
stature,
premature aging
Progeroid syndromes (PS) are a group of rare genetic disorders that mimic physiological aging, making affected individuals appear to be older than they are. The term ''progeroid syndrome'' does not necessarily imply progeria ( Hutchinson–Gilfo ...
, and increased risk of
malignant disease".
* Some individuals trisomic for chromosome 8 were deficient in production of
coagulation factor VII due to a factor 7 regulation gene (F7R) mapped to 8p23.3-p23.1.
* Trisomy and other rearrangements of chromosome 8 have also been found in
tricho–rhino–phalangeal syndrome.
* Small regions of chromosome 8 trisomy and monosomy are also created by
recombinant chromosome 8 syndrome (
San Luis Valley syndrome), causing anomalies associated with
tetralogy of Fallot
Tetralogy of Fallot (TOF), formerly known as Steno-Fallot tetralogy, is a congenital heart defect characterized by four specific cardiac defects. Classically, the four defects are:
* pulmonary stenosis, which is narrowing of the exit from the r ...
, which results from recombination between a typical chromosome 8 and one carrying a parental
paracentric inversion
An inversion is a chromosome rearrangement in which a segment of a chromosome becomes inverted within its original position. An inversion occurs when a chromosome undergoes a two breaks within the chromosomal arm, and the segment between the two br ...
.
* Trisomy is also found in some cases of
chronic myeloid leukaemia
Chronic myelogenous leukemia (CML), also known as chronic myeloid leukemia, is a cancer of the white blood cells. It is a form of leukemia characterized by the increased and unregulated growth of myeloid cells in the bone marrow and the accumulati ...
, potentially as a result of karyotypic instability caused by the
bcr:abl fusion gene A fusion gene is a hybrid gene formed from two previously independent genes. It can occur as a result of translocation, interstitial deletion, or chromosomal inversion. Fusion genes have been found to be prevalent in all main types of human neopl ...
.
Diagnosis
The simplest and easiest way to detect trisomy 8 is by a
karyotype
A karyotype is the general appearance of the complete set of metaphase chromosomes in the cells of a species or in an individual organism, mainly including their sizes, numbers, and shapes. Karyotyping is the process by which a karyotype is disce ...
, a photograph representing all chromosomes of a cell in an orderly manner.
Amniocentesis is also a technique for diagnosis. Samples from the amniotic fluid are taken from a fetus, cultured, then analyzed by a karyotype. If the photograph shows 3 copies of chromosome 8 instead of 2, then the individual has trisomy 8.
See also
*
Warkany syndrome 1
References
External links
U.S. National Library of Medicine: Warkany Syndrome 2{{Chromosomal abnormalities
Autosomal trisomies
Syndromes