Down Syndrome Handout

What is Down Syndrome?

Down Syndrome is the most common chromosomal abnormality of a generalized syndrome, occurring in 1 in 800 to 1000 live births. It is also the most prevalent genetic abnormality associated with mental retardation.

Down Syndrome most commonly results from the presence of an extra #21 chromosome, thus the name Trisomy 21. This means there are 47 chromosomes instead of the usual 46 chromosomes in each cell. The extra chromosome is associated with a number of physical and cognitive characteristics which together make up Down Syndrome.

How do Children with Down Syndrome Develop?

Most children with Down Syndrome are developmentally delayed and have greater difficulty learning that their peers. However, it is not possible to predict the degree of progress or delay in any individual child at birth. Individual children with Down Syndrome vary in achievement and development similarly to any other group of children. Infant stimulation and special education programs contribute greatly toward helping Down Syndrome children reach their individual maximum potentials. The most beneficial setting is in the presence of other children, at home in the family as well as at school.

Nurses working with these families need to be aware of the types of programs in their community. Under Public Law 101-476, the Individuals with Disabilities Act of 1990, states are encour4aged to provide full early intervention services and are required to provide educational opportunities for all children with disabilities from birth to 21 years of age.

Websites:

National Assoc. for Down Syndrome

The Arc—an association for persons w/ disabilities
Easter Seals homepage

Can People with Down Syndrome be Expected to Work?

Contrary to past assumptions many individuals are capable of working in the competitive labor market in a variety of jobs ranging from stock clerk to laboratory aide. Even individuals with severe disabilities can maintain competitive employment when provided appropriate training, follow-up and support. Public schools and adult service providers are now beginning to collaborate on preparing all youth with mental retardation to make the transition from school to work and life in the community. Vocational training that prepares them for as independent a life-style as possible within their scope of abilities is strongly encouraged as children grow older.

What is the Potential for Adults with Down Syndrome?

In adolescence and early adulthood people with Down Syndrome are frequently as eager to leave home as many other young people. They may choose to live in group homes, semi-independent supported apartments or other community living arrangements. They should be employed in the community to the extent they are capable with support as needed. They also should be provided assistance to participate in recreational and leisure activities in the community alongside everyone else.

What are the Identifiable Physical Characteristics of Down Syndrome? (p.834, 10th ed)

Nearly 50 physical characteristics associated with Down Syndrome have been identified. However, most individuals with Down Syndrome do not possess all characteristics. Some of the most common physical signs of Down Syndrome include:

  • Eyes: slanting eyes (oblique palpebral fissures) with a fold of skin at the inner corners (epicanthal folds);
  • Nose: a low nasal bridge and a small nose which give the face a flattenedappearance;
  • Ears: small, short pinna; low set;
  • Hands: transverse palmar crease (Simian crease); broad and short with stubby fingers, incurved little finger
  • Musculoskeletal: Hyperflexibility, Hypotonia which predisposes children to frequent URI R/T inability to cough effectively.
  • Mouth: High, arched, narrow palate; protruding tongue
  • Neurological: lack of Moro Reflex

What are the Genetic Variations Associated With Down Syndrome?

The three most prevalent genetic variations which result in Down Syndrome include:

  • Trisomy 21: Trisomy 21 is present in approximately 95% of people with Down Syndrome. During creation of either the egg or the sperm, a misdivision occurs resulting in the presence of an extra chromosome. Upon conception, a cell with 47 chromosomes is created. If the extra chromosome is chromosome #21, that child is said to have Down Syndrome. Although children with Trisomy 21 are born to parents of all ages, there is statistically greater risk in older women, particularly those over 35 years of age.
  • Translocation: Translocation is present in 3-4% of all cases. Translocation involves the breakage of chromosome #21 during the creation of either the sperm of the egg and the subsequent attachment of the broken piece to either chromosome #14, #21, or #22. Upon conception, a cell with translocated piece of chromosome #21 is created. This type is usually hereditary and not associated with increased parental age.
  • Mosaicism: Mosaicism is an extremely rare chromosomal disorder which occurs in approximately 1-2% of persons with Down Syndrome. Here, an incomplete cell division occurs after conception rather than before conception as in the cases of Trisomy 21 and Translocation. Since an incomplete division occurs after conception, not all of the cells subsequently created by replication have an extra chromosome. Thus a mosaic is created with some cells having 46 chromosomes and others having 47 chromosomes. The intensity of characteristics varies with the number of cells having an extra chromosome.

What health problems are associated with Down Syndrome?

  • Cardiovascular Disease: Many of these children have congenital heart malformations, the most common being septal defects.
  • Respiratory tract infections: Hypotonicity of the chest and abdominal muscles and dysfunction of the immune system probable predispose to the development of respiratory tract infection.
  • Thyroid Dysfunction: frequently congenital Hypothyroidism.
  • Leukemia: increased risk of development
  • Alzheimer disease: The relationship between Down Syndrome and Alzheimer disease is still unclear. The appearance of structural changes identical to those of individuals with Alzheimer disease in the brains of all individuals with Down Syndrome over the age of 36 has suggested a relationship.
  • Skeletal abnormalities: Skeletal abnormalities include a small skull, small facial bones, abnormal ribs, abnormal pelvic structure and atlantoaxial instability. Atlantoaxial instability is diagnosed when the fist two vertebrae in the neck have an increased mobility. People with this condition have a greater than average chance of spinal cord injury due to the shifting of the vertebrae during activity.

What is the life expectancy for People with Down Syndrome?

Due to the increase in medical knowledge and medical technology, the average life expectancy of individuals with Down Syndrome has risen in recent years, but is still lower than that for the general population. >80% survive to age 30 years and beyond.

How can Down Syndrome be detected?
Screening tests include:

  • Nuchal translucency testing. This test, performed between 11 and 14 weeks of pregnancy, uses ultrasound to measure the clear space in the folds of tissue behind a developing baby's neck. (Babies with DS and other chromosomal abnormalities tend to accumulate fluid there, making the space appear larger.) This measurement, taken together with the mother's age and the baby's gestational age, can be used to calculate the odds that the baby has DS. Nuchal translucency testing correctly detects DS about 80% of the time; when performed with a maternal blood test, it may offer greater accuracy.
  • The triple screen (also called the multiple marker test) and the alpha fetoprotein plus. These tests measure the quantities of various substances in the mother's blood, and together with the woman's age, estimate the likelihood that her baby has Down syndrome. They are typically offered between 15 and 20 weeks of pregnancy.
  • A detailed ultrasound. This is often performed in conjunction with the blood tests, and it checks the fetus for some of the physical traits associated with Down syndrome. However, these screening tests are only about 60% accurate and often lead to false-positive or false-negative readings.

Diagnostic tests include:

  • Amniocentesis. This test, performed between 16 and 20 weeks of pregnancy, involves the removal of a small amount of amniotic fluid through a needle inserted in the abdomen. The cells can then be analyzed for the presence of chromosomal abnormalities. Amniocentesis carries a small risk of complications, such as preterm labor and miscarriage.
  • Chorionic villus sampling (CVS). CVS involves taking a tiny sample of the placenta, also through a needle inserted in the abdomen. The advantage of this test is that it can be performed earlier than amniocentesis, between 8 and 12 weeks. The disadvantage is that it carries a slightly greater risk of miscarriage and other complications.
  • Percutaneous umbilical blood sampling (PUBS). Usually performed after 20 weeks, this test uses a needle to retrieve a small sample of blood from the umbilical cord. It carries risks similar to those associated with amniocentesis. retrieved 8/1/07.

References:
Hockenberry et al. (2008). Wong’s Nursing Care of Infants & Children. (8th ed.) Mosby: St. Louis