Etiology Ppp

Embed Size (px)

Text of Etiology Ppp

  • 8/12/2019 Etiology Ppp










  • 8/12/2019 Etiology Ppp


    The cause is unknown and multiple theories exist.

    Down syndrome(DS) is a genetic disorder that iscaused by an extra chromosome 21 that is present in

    all or some of the individual's cells.

    There are three types of


    abnormalities in Down



  • 8/12/2019 Etiology Ppp


    The first is called trisomy 21 and is themost common form of DS. With trisomy

    21, the individual has an extra

    chromosome 21, which results in a totalof 47 chromosomes in each cell rather

    than the typical 46.


  • 8/12/2019 Etiology Ppp


    The second is called mosaicism and

    is the least common form of DS. In

    this case, only some of the cells

    contain 47 chromosomes, while the

    other cells contain an accurate 46.


  • 8/12/2019 Etiology Ppp


    The third type is called

    translocation where the extra

    chromosome attaches (or

    translocates) to a different

    chromosome, such as 14 or 22.


  • 8/12/2019 Etiology Ppp


    The additional chromosome is almost always the result of faulty

    cell division, in either the egg or sperm, resulting in 3 chromosome

    21s (2 from the egg and 1 from the sperm, or vice-versa). Though

    the extra chromosome could come from either the father or the

    mother, only 5% of the cases have been traced to the father.Women age 35 years and older have a significantly increased

    chance of having a child with DS, however, 80% of children born

    with DS are actually born to mothers under the age of 35 years due

    to higher fertility rates.

    DS is one of the most common chromosome


    It is estimated that the incidence is between 1 in 800 to 1,000

    live births. There are approximately 350,000 individuals in theUnited States with DS. It occurs in all racial, ethnic, and

    socioeconomic groups. Recent research shows that slightly

    more males than females are born with DS in comparison

    with the general population. 6

  • 8/12/2019 Etiology Ppp


    Down syndrome was first accurately described in 1866 by an

    English physician named John Langdon Down. Then, in 1959, a

    French physician named Jerome Lejeune identified Down

    syndrome as a chromosome anomaly. It was Lejeune who

    observed 47 chromosomes in individuals with DS, rather than 46


    The cause of DS is not known, however, some experts believe thathormonal abnormalities, x-rays, viral infections, immunological

    problems, or genetic predisposition may be the cause of improper

    cell division, resulting in the syndrome.

    What is known, is that the extra chromosome 21 causes an extra

    dose of some proteins, which causes the typical features of thesyndrome. In addition, it should be noted that DS is not the result

    of something that either parent did or did not do.


  • 8/12/2019 Etiology Ppp


    Risk factors include:

    Advancing maternal age.A woman's chances of giving birth to a

    child with Down syndrome increase with age because older eggs

    have a greater risk of improper chromosome division. By age 35, a

    woman's risk of conceiving a child with Down syndrome is 1 in 400.

    By age 45, the risk is 1 in 35. However, most children with Down

    syndrome are actually born to women under age 35 because

    younger women have far more babies.

    Having had one child with Down syndrome.Typically, a woman

    who has one child with Down syndrome has about a 1 percent

    chance of having another child with Down syndrome.

    Being carriers of the genetic translocation for Downsyndrome.Both men and women can pass the genetic

    translocation for Down syndrome on to their children.


  • 8/12/2019 Etiology Ppp



    The Chromosomes

  • 8/12/2019 Etiology Ppp


    Chromosomes are thread-like structures composed of DNA and other

    proteins. They are present in every cell of the body and carry the

    genetic information needed for that cell to develop. Genes, which areunits of information, are "encoded" in the DNA.

    Human cells normally have 46 chromosomes which can be arranged

    in 23 pairs. Of these 23, 22 are alike in males and females; these are

    called the "autosomes." The 23rd pair are the sex chromosomes ('X'

    and 'Y').

    Each member of a pair of chromosomes carries the same information,

    in that the same genes are in the same spots on the chromosome.

    However, variations of that gene ("alleles") may be present. (Example:

    the genetic information for eye color is a "gene;" the variations forblue, green, etc. are the "alleles.")


  • 8/12/2019 Etiology Ppp


    So, normal eggs and sperm cells only have 23chromosomes, when they come together there are 46.


    Human cells divide in two ways. The first is ordinary cell

    division ("mitosis"), by which the body grows. In this

    method, one cell becomes two cells which have the exactsame number and type of chromosomes as the parent

    cell. The second method of cell division occurs in the

    ovaries and testicles ("meiosis") and consists of one cell

    splitting into two, with the resulting cells having half the

    number of chromosomes of the parent cell.

  • 8/12/2019 Etiology Ppp


    This is what a normal set of

    chromosomes looks like.Note the 22 evenly paired

    chromosomes plus the sex


    The XX means that this person

    is a female.

    The test in which blood or skin

    samples are checked for the

    number and type of

    chromosomes is called a

    karyotype, and the results look

    like this picture.


  • 8/12/2019 Etiology Ppp


    Many errors can occur during cell division. In meiosis, the pairs of

    chromosomes are supposed to split up and go to different spots in the

    dividing cell; this event is called "disjunction." However, occasionally one pair

    doesn't divide, and the whole pair goes to one spot. This means that in the

    resulting cells, one will have 24 chromosomes and the other will have 22


    This accident is called "nondisjunction." If a sperm or egg with an abnormalnumber of chromosomes merges with a normal mate, the resulting fertilized

    egg will have an abnormal number of chromosomes. In Down syndrome,

    95% of all cases are caused by this event: one cell has two 21st

    chromosomes instead of one, the other normal cell has one, so the

    resulting fertilized egg has three 21st chromosomes. Hence the scientific

    name, trisomy 21.


  • 8/12/2019 Etiology Ppp


    Recent research has shown that in these cases,

    approximately 90% of the abnormal cells are the eggs.

    The cause of the nondisjunction error isn't known, but

    there is definitely connection with maternal age.

    Research is currently aimed at trying to determine the

    cause and timing of the nondisjunction event.


  • 8/12/2019 Etiology Ppp


    Here's the karyotype of a male with trisomy 21:

    Three to four percent of all cases of trisomy 21 are due to

    Robertsonian Translocation.

    In this case, two breaks occur in separate chromosomes, usually the 14th

    and 21st chromosomes. There is rearrangement of the genetic material

    so that some of the 14th chromosome is replaced by extra 21st


    So while the number of chromosomes remain normal, there is a

    triplication of the 21st chromosome material. Some of these children may

    only have triplication of part of the 21st chromosome instead of the whole

    chromosome, which is called a partial trisomy 21.

    Translocations resulting in trisomy 21 may be inherited, so it's importantto check the chromosomes of the parents in these cases to see if either

    may be a "carrier."


  • 8/12/2019 Etiology Ppp


  • 8/12/2019 Etiology Ppp




    Low muscle tone

    Flat facial profile (depressed nasal bridge and smallnose)

    Flattening of the back of the head

    Small hands and feet

    An upward slant of the eyes

    An abnormal shape of the ear

    A single deep crease across the center of the palm

    An excessive ability to extend the joints

    Fifth finger has one flexion furrow instead of two

    Small skin folds on the inner corner of the eyes

    Excessive space between large and second toe

    Enlargement of tongue in relation to the size of the

    mouth Mental retardation (can range from very mild to

    severe, however, is typically mild to moderate)

    Speech delays

    Short stature

    There are many physicalcharacteristics that are associated withDS. Not every individual has all thecharacteristics, however, the followingis a list of the most common traits:

  • 8/12/2019 Etiology Ppp



  • 8/12/2019 Etiology Ppp


    Congenital heart defects

    Increased susceptibility to infection

    Respiratory problems

    Obstructed digestive tracts

    Hearing deficits

    Eye problems such as cataracts and

    strabismus Failure to thrive in infancy and obesity in


    Thyroid dysfunctions

    Skeletal problems (hip dislocations,atlantoaxial instability)

    Increased risk of developing Alzheimer's

    disease (over age 35) and leukemia

    In addition to the common characteristics, a child with DS may

    also have the following medical issues:


  • 8/12/2019 Etiology Ppp


    Nursing Management:

    1. Assess for associated problems.

    2. Administer medications which maybe prescribed for associated


    3. Implement a plan of care that is the same as for mental retardation.

    Include planning and intervention strategies for associated problemsand features.

    4. Encourage genetic counseling.

    5. Explain hypertonicity and joint hyperextensibility to parents, and that

    the childs resultant lack of clinging is physiologic and not a sign ofdetachment.


  • 8/12/2019 Etiology Ppp


    6. Prevent respiratory infections by clearing the nose with a bulbsyringe, using a cool mist vaporizer, performing chest physiotherapy

    when needed, providing good handwashing and avoiding exposure

    to infection.

    7. When feeding infants and young children, use a small, straight-

    handled spoon to push food to the side and back of the mouth.Feeding difficulties occur due to a protruding tongue and hypotonia.

    8. Encourage fluids and foods rich in fiber. Constipation results from

    decreased muscle tone, which affects gastric motility.

    9. Provide good skin care because the skin is dry and prone toinfection.

    Nursing Management: continued:


  • 8/12/2019 Etiology Ppp


    An amniocentesesis the prenatal procedure to diagnose

    Down Syndrome. A chromosome test can be done after



    Generally, when a child is born with Down syndrome, the appearance

    of the child is the first indication that he or she may have the disorder.

    Therefore, a chromosome analysis is conducted which looks for three

    chromosome 21s or variants as described above. It can also be

    diagnosed prenatally by either an amniocentesis or chorionic villus



  • 8/12/2019 Etiology Ppp



    There is no cure for DS, however, early intervention programs, preschools,

    and integrated education can be very beneficial for the child with DS.

    With the proper education, many children with DS will learn to read, write,

    and participate in school activities. In addition to receiving an early

    education, children with DS may benefit from several therapies as well.

    Due to the delays in speech that are commonly seen in children with downsyndrome, speech therapy is beneficial. The speech pathologist should

    emphasize adequate development of oral muscles used in feeding and

    speech articulation, and to focus on developing expressive and receptive

    skills to enhance communicative functioning. Due to the low tone found in

    children with DS, physical therapy may be useful in improving gross motor

    skills such as sitting and walking and improving postural alignment.


  • 8/12/2019 Etiology Ppp


    Finally,children with DS may also benefit from occupational

    therapy to develop fine-motor skills, self help skills, upper extremity

    strength, and coordination.