Down Syndrome (Trisomy 21; 47,XX,+21 or 47,XY,+21)

Genetic Materials 2008 Nucleus Medical Art, Inc. Risk Factors A risk factor is something that increases your chance of getting a disease or condition. Genetics: If either parent is a carrier of a specific type of Down syndrome (Translocation Down Syndrome), there is an increased risk of giving birth to a child with this type of Down syndrome.Age: The chance of having a child with Down syndrome increases after a woman reaches age 35.Sex: More boys than girls are born with Down syndrome. Relationship of Down Syndrome Incidence to Mother's AgeResearchers have established that the likelihood that a reproductive cell will contain an extra copy of chromosome 21 increases dramatically as a woman ages. Therefore, an older mother is more likely than a younger mother to have a baby with Down syndrome. Older mothers account for only about 9% of all live births each year, but for 25% of Down syndrome births.Mother's Age (Years)Incidence of Down SyndromeUnder 30Less than 1 in 1,000301 in 900351 in 400361 in 300371 in 250381 in 180391 in 135401 in 105421 in 60441 in 35461 in 20481 in 16491 in 12 Hook, EG, Lindsjo A. Down syndrome in live births by single year maternal age interval in a Swedish study: comparison with results from a New York State study. Am J Hum Genet. 1978;30:19-27.

Symptoms Infants born with Down syndrome may have some or all of the following physical characteristics: Muscle hypotonia, low muscle toneFlat facial features, a somewhat depressed nasal bridge and a small noseUpward slanted eyes, small skin folds on the inner corner of the eyesShort neckMisshaped earsWhite spots on the colored part of the eyeSingle skin crease in the palm of the handExcess flexibility in jointsHeart defectsSight and hearing problemsLarge and protruding tongueFifth finger has one flexion furrow instead of twoExcessive space between large and second toe The degree of medical problems and mental retardation varies. Talents, abilities, and pace of development differ. People with Down syndrome may be born with or develop: Vision problemsHearing lossHeart defects Increased incidence of acute leukemiaFrequent ear infections and increased susceptibility to infection in generalGastrointestinal obstruction (imperforate anus and similar problems)Esophageal atresia or duodenal atresiaOne third of patients experience blocked airways during sleep Increased incidence of dementia in older ages Instability of the back bones at the top of the neck, can result in compression injury of the spinal cordUrinary system defectsHigh blood pressure in the lungs Seizures An under-active thyroid ( hypothyroidism ) Slow growthLate to sit, walk, toilet trainSpeech problemsObesityEmotional problemsRisk that others assume that a child is more retarded than he or she is Most of these health problems are treatable, and the majority of people born with Down syndrome today have a life expectancy of approximately 55 years.

Diagnosis Prenatal DiagnosisThere are two types of procedures available to pregnant women: screening tests and diagnostic tests. Screening tests estimate the risk of the fetus having Down syndrome; diagnostic tests tell whether or not the fetus actually has the condition. Screening Tests: Triple Screen and Alpha-fetoprotein PlusThese tests measure quantities of various substances in the blood (alpha-fetoprotein, human chorionic gonadotropin, and unconjugated estriol). Together with the woman's age, the doctor can estimate the risk of having a child with Down syndrome. These screening tests have traditionally been offered between 15 and 20 weeks of gestation, but new data suggests that optimal screening should begin as early as 11 weeks and include both ultrasound imaging and blood screening. For maximum test sensitivity, screening should be done at 11 weeks with a follow-up in the second trimester for those who screen negative. Recent data reports Down syndrome detection rates of up to 96% for combined first and second trimester screening. Five percent of women who undergo these tests will be given false-positive readings. As a consequence, they may choose to have diagnostic testing done, which could result in a miscarriage or other harm to a normal fetus. Diagnostic Tests The procedures available for prenatal diagnosis of Down syndrome are chorionic villus sampling (CVS), amniocentesis , and percutaneous umbilical blood sampling (PUBS). Each one of these procedures carries a small risk of miscarriage as tissue is extracted from the placenta or the umbilical cord to examine the fetus' chromosomes.The procedures are about 98% to 99% accurate in the detection of Down syndrome.Amniocentesis is usually performed between 12 and 20 weeks of gestation, CVS between 10 and 12 weeks, and PUBS after 20 weeks. Post-Natal DiagnosisDoctors can also usually identify a child born with Down syndrome at delivery. When features that suggest Down syndrome are present, a blood test will be done for chromosome study and a definitive diagnosis.

TreatmentThere is no cure for Down syndrome. Some newborns may need surgery to repair serious medical problems, like heart defects. Living at home and receiving special therapy helps children with Down syndrome achieve their full potential. Most people with the condition can actively participate in the communityat schools, jobs, and various leisure activities. Some live with family, some with friends, and some independently. Baby CareInfants with Down syndrome may take longer to feed. A child with the condition will start talking, playing, and performing other activities later than normal. EducationSchool programs designed to meet the child's special needs may help to increase learning opportunities. Children who have accomplished academic milestones may be mainstreamed into regular public school classes, with additional support as required. Rehabilitation ServicesSpeech, physical, and occupational therapy may improve the ability to speak, walk, and perform activities of daily living. Social ServicesProfessional support helps a family cope with caring for a child with birth defects and mental retardation. Mental health professionals offer help with managing emotional problems. PreventionThere are no guidelines for preventing Down syndrome. If you have concerns about having a child with Down syndrome, consider getting genetic counseling prior to becoming pregnant.

RESOURCES: National Down Syndrome Congresshttp://www.ndsccenter.org National Down Syndrome Societyhttp://www.ndss.org CANADIAN RESOURCES: Canadian Down Syndrome Societyhttp://www.cdss.ca/site/about_us/welcome.php Public Health Agency of Canadahttp://www.phac-aspc.gc.ca/ References: Malone FD, Canick JA, Ball RH, et al. First- and second-trimester evaluation of risk (FASTER) research consortium. First-trimester or second-trimester screening, or both, for Down's syndrome. N Engl J Med . 2005;353:2001-2011. MedlinePlus. National Library of Medicine website. Available at: http://www.nlm.nih.gov/medlineplus/downsyndrome.html . National Down Syndrome Society website. Available at: http://www.ndss.org . National Institute of Child Health and Human Development website. Available at: http://www.nichd.nih.gov/publications/pubs/downsyndrome/down.cfm . Last reviewed October 2007 by Mark A. Best, MD, MPH, MBA, FCAP, FASCPPlease be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.