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Down syndrome

Down syndrome. Diagnosic method. A newborn baby with Down syndrome often has physical features a flat facial profile an upward slant to the eye a short neck abnormally shaped ears white spots on the iris of the eye. Diagnostic method. blood test called a chromosomal karyotype

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Down syndrome

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  1. Down syndrome

  2. Diagnosic method A newborn baby with Down syndrome often has physical features • a flat facial profile • an upward slant to the eye • a short neck • abnormally shaped ears • white spots on the iris of the eye

  3. Diagnostic method • blood test called a chromosomal karyotype • This involves "growing" the cells from the baby's blood for about two weeks, followed by a microscopic visualization of the chromosomes to determine if extra material from chromosome 21 is present.The baby is down syndrome.

  4. Maternal Serum Screening • checking the mother’s blood • There are three independent measurements: alpha-fetoprotein (AFP), unconjugated estriol (uE3) and human chorionic gonadotropin (hCG). • Alpha-fetoprotein is made in the part of the uterus called the yolk sac and in the fetal liver, and some amount of AFP gets into the mother's blood. In neural tube defects, the skin of the fetus is not intact and so larger amounts of AFP is measured in the mother's blood. In Down syndrome, the AFP is decreased in the mother's blood, presumably because the yolk sac and fetus are smaller than usual.

  5. Estriol is a hormone produced by the placenta, using ingredients made by the fetal liver and adrenal gland. Estriol is decreased in the Down syndrome pregnancy. This test may not be included in all screens, depending on the laboratory. • Human chorionic gonadotropin hormone is produced by the placenta, and is used to test for the presence of pregnancy. A specific smaller part of the hormone, called the beta subunit, is increased in Down syndrome pregnancies. • consideration in the screening test is the age of the fetus (gestational age).

  6. Other diagnostic methods • These tests include amniocentesis, chorionic villus sampling (CVS), and percutaneous umbilical blood sampling (PUBS).

  7. Amniocentesis • Is the removal and analysis of a small sample of fetal cells from the amniotic fluid, is widely available and involves a lower risk of miscarriage than chorionic villus sampling. However, amniocentesis cannot be done until the 14th to 18th week of pregnancy, and it usually takes additional time to determine whether the cells contain extra material from chromosome 21.

  8. Side effects to the mother include cramping, bleeding, infection and leaking of amniotic fluid afterwards • slight increase in the risk of miscarriage

  9. Chorionic villus sampling • Conducted at 9 to 11 weeks of pregnancy, involves extracting a tiny amount of chorionic villi, tissue extensions that will eventually develop into a placenta. The tissue can be tested for the presence of extra material from chromosome 21. The villi can be obtained through the pregnant woman's abdomen or cervix. This type of sampling carries a 1-2% risk of miscarriage.

  10. percutaneous umbilical blood sampling or PUBS • Is the most accurate method and can be used to confirm the results of CVS or amniocentesis. However, PUBS cannot be performed until later in the pregnancy, during the 18th to 22nd weeks, and carries the greatest risk of miscarriage.

  11. New prenatal diagnostic techniques • Are currently being developed. The NICHD has supported the development of a new, noninvasive test performed during the first trimester of pregnancy, that samples and separates fetal cells from the mother's blood. The goal is to compare the accuracy of this type of cellular level analysis with results obtained by amniocentesis or CVS.

  12. Background information of Down Syndrome • most frequently occurring chromosomal abnormality occurs once in about every 800 to 1000 live births and in families from all social, economic, cultural, religious and racial backgrounds • there are approximately 80 newborn babies in Hong Kong found to be suffered from Down syndrome each year • if a couple has a child with Down syndrome, there is usually an increased risk for a second affected child • the likelihood of this occurring increases with the age of the mother

  13. Down Syndrome characteristic • Low intelligence • Flattened back of head • Slightly shortened fingers • The little finger curves inward • Some have open-heart surgery, then make a chest scar after operation

  14. What is Down Syndrome • a genetic abnormality caused by the presence of extra chromosome 21 materials • was named after john Langdon down, a British physician, who first described it in 1866 • cause of this condition is still unknown • there are three types of chromosomal patterns that result in Down syndrome. They are trisomy 21, translocation and mosaicism

  15. Trisomy 21 • most common (95%) • due to a mutation in chromosome number • caused by meiotic non-disjunction (i.e. unequal chromosome division)of the chromosome pair 21 during the production of ova • Fusion of ovum, which contain 24 chromosomes, with normal sperm having 23 chromosomes, will result in offspring having 47 chromosomes in all cell

  16. Translocation • less common (3-5%) • due to a mutation in chromosome structure • cause by the translocation of part or all of chromosome 21 to another chromosome, usually 14 • indistinguishable from individuals with the trisomy 21 form

  17. Mosaicism • approximately 2% of people • A faulty cell division occurs in one of the early cell division after conception, resulting in some cells having 46 chromosomes and some having 47 • the percentage of cells with 47 chromosomes instead of 46 varies from person to person. Those cells with 47 chromosomes contain an extra 21st chromosome • Because of the “mosaic” pattern of the cells, the term mosaicism is used

  18. What Is Genetic Counseling Genetic counseling is the process of: • Evaluating family history and medical record • Ordering genetic tests • Evaluating the results of this investigation • Helping parents understand and reach decisions about what to do next

  19. Counseling • While caring for a child with Down syndrome frequently requires more time and energy, parents of newborn children with Down syndrome should seek the advice of a knowledgeable pediatrician and/or the many Down syndrome support groups and organizations available.So they have already to care the children who have down syndrome

  20. Importances of genetic counseling & genetic screening • Detect the risk of having a specified fetal abnormality • Limitation of the diagnostic test • Conveyed to the couple in a manner they can understand • Options open to the couple should a fetal abnormality is detected

  21. Example of counseling center • Administration on Developmental DisabilitiesAdministration for Children and FamiliesU.S. Department of Health and Human ServicesMail Stop: HHH 300F370 L’Enfant Promenade S.W.Washington, DC 20447(202) 690-6590 • http://www.acf.dhhs.gov/programs/add/http://www.acf.dhhs.gov/programs/add/ • American Speech, Language and Hearing Association10801 Rockville PikeRockville, MD 208521-800-638-8255 or 1-888-321-ASHA • http://www.asha.org/http://www.asha.org/

  22. Learning Disabilities Association of America4156 Library RoadPittsburgh, PA 15234-1349(412) 341-1515 or 1-888-300-6710 • http://www.ldanatl.org/http://www.ldanatl.org/ • March of Dimes1275 Mamaroneck AvenueWhite Plains, NY 10605(914) 428-71001-888-MODIMES (1-888-663-4637) • http://www.modimes.org/http://www.modimes.org/ • More counseling center:http://www.nichd.nih.gov/publications/pubs/downsyndrome/down.htm - AdditionalResources

  23. Genetic screening These tests identify the likelihood of passing certain genetic diseases or disorders (those caused by a defect in the genes -the tiny, DNA-containing units of heredity that determine the characteristics and functioning of the entire body) to your children. • Down syndrome • Cystic fibrosis • Tay-Sachs disease (a fatal disease affecting the central nervous system) Genetic disorders are:

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