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Friday, Jan 09, 2009 | 01:15 PM
Madisons Foundation - Moms And Dads In Search Of Needed Support
Trisomy 8
Sunday, 31 August 2003
Last Updated Tuesday, 17 February 2004
What
Trisomy 8 syndrome is a genetic condition in which some or all of the cells in the body have three copies of chromosome 8 instead of the usual two. cells, the building blocks of the human body, are home to the genetic information, or blueprints, that determine all of our physical characteristics. These genes are organized into chromosomes, of which there are 23 pairs. Normally, there are two copies of each chromosome. Occasionally, the genes are altered which cause genetic disorders in the child.Who
There are two forms of trisomy 8: complete or mosaic. When all of the cells in the body have three copies of chromosome 8, it is called “complete trisomy 8”. Complete trisomy 8 is generally not compatible with life and accounts for 0.8% (1 out of 125) of miscarriages. When some of the cells in the body have three copies of chromosome 8, and the other cells have the normal two copies of chromosome 8, it is called “trisomy 8 mosaicism”. The infant born with trisomy 8 mosaicism is extraordinarily rare, yet there are some who have lived to adulthood. By current report, there have been only around one hundred individuals with trisomy 8 worldwide.Signs and Symptoms
Individuals can have an extremely wide variability of features associated with trisomy 8 depending on their degree of mosaicism. The more cells that are normal, the milder the symptoms. The more cells that are trisomy 8, the more severe the symptoms. An affected child can have mental retardation, although this may be mild. The appearance of his or her face may include: a high forehead; squinting eyes (because the eye muscles are paralyzed); a broad nose; abnormally shaped ears which may be large or long; thick lips; pouting out of the lower lip; abnormal palate (or roof of the mouth); and/or a small lower jaw. The child’s bones may be affected causing a short neck; long rib-cage (because of an abnormal number of ribs); narrow, sloping shoulders; scoliosis or curvature of the spine; short or abnormal bending of the fingers; narrow hip bones; and/or absent or abnormal knee caps. There may be deep creases in the palms of the hands and the soles of the feet. The child may have extra nipples, abnormal kidneys or genitalia; and/or heart problems. Trisomy 8 has been associated with various cancers.Possible Causes
Each pair of chromosomes is made up of one chromosome from the mother’s egg and one chromosome from the father’s sperm. Complete trisomy 8 occurs when the mother’s egg and the father’s sperm combine, and instead of resulting in two copies of chromosome 8, the baby inherits an extra copy for a total of three. cells destined to become eggs or sperm have to go through a unique process called meiosis. Normal cells in the body have 46 chromosomes (23 pairs), and must divide so that when the egg and sperm combine the baby has the right amount of genetic material. If this division does not go as it should, then an extra copy of chromosome 8 is left and the baby ends up with one extra chromosome 8. Recent research indicates that the extra copy of chromosome 8 comes from the father’s sperm: the egg contributes one chromosome 8 and the sperm contributes two. Since all of the body’s cells are derived from the egg and sperm, then all of the cells will have trisomy 8 (complete trisomy 8). The cause of trisomy 8 mosaicism is different. Instead of the extra chromosome 8 coming from the egg or the sperm, the extra chromosome 8 occurs because of a mistake in the growing cells of a developing fetus’ body. Trisomy 8 mosaicism means that the genetic abnormality occurs after fertilization and therefore does not affect all cells like complete trisomy 8. The signs and symptoms associated with trisomy 8 mosaicism are proportional to the amount of cells that are abnormal. Recent research indicates that trisomy 8 mosaicism can also arise secondary to a process called tumorigenesis (which means development of new growths, such as a tumor). cancer cells often replicate uncontrollably and may make mistakes. A mistake that involves the inclusion of an extra chromosome 8 may allow a tumor to evolve into a specific type of cancer such as, childhood acute lymphocytic leukemia (ALL), acute myelocytic leukemia (AML), chronic myelocytic leukemia (CML), invasive breast carcinoma, ovarian carcinoma, or myelocytic malignancies.Diagnosis
Prenatal testing such as amniocentesis and ultrasound can detect trisomy 8. A sample of the amniotic fluid surrounding the fetus is examined for the number of chromosomes that the developing baby has. ultrasound is an imaging study which can show some of the physical features of the developing baby that are described above in the signs and symptoms section.Treatment
A child with trisomy 8 mosaicism may need to be treated surgically for abnormalities of his or her heart, kidney, or genitourinary system. On the other end of the mosaic spectrum, a mildly affected child may be treated the same way one would treat a normal child. It is important to raise a special child in an encouraging and supportive environment. Some individuals may benefit from psychological counseling as well as academic support to avoid depression, social isolation, and difficulties in school. Adults with this chromosomal abnormality should speak with a geneticist if they are thinking about becoming pregnant or having children because this may be passed onto their children.Prognosis
Mortality (death) is high during pregnancy, so complete trisomy 8 is rarely seen at birth. Therefore, trisomy 8 is almost always associated with mosaicism in live births. Due to the nature of mosaicism, symptoms are highly variable among individuals. While some will never be diagnosed due to the low number of affected cells, others will struggle with mental and physical handicaps. Lifespan and quality of life is also highly dependent on the degree of mosaicism. It should be noted that reproduction in females with mosaic trisomy 8 is possible, though uncommon.Connect with other parents
In the spirit of community and support, Madisons Foundation offers the unique service of connecting parents of children with rare diseases. If you would like to be connected to other parents of children with this disease, please fill out this brief form.Weblinks
http://www.geocities.com/Heartland/Creek/4425/
A good site with information about Trisomy 8 as well as a support group network. There is also information about masaicism, a pamphlet on the parents' persepctive, accounts from other families with trisomy 8 children, and clear definitions to genetics terms.