Etiology Ppp

8/12/2019 Etiology Ppp

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ETIOLOGY

ALCAIDE, JONALYN

ANGEL, PHOEBE

BASUIL, ROBELYN

BILANGO, ROVELYNCABILDO, LUDY

CACAMO, HILDA

CADAOAS, MARY JOY

FLORAGUE, CRESTITA


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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

chromosome

abnormalities in Down

syndrome.

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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.

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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.

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The third type is called

translocation where the extra

chromosome attaches (or

translocates) to a different

chromosome, such as 14 or 22.

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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

abnormalities.

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


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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

chromosomes.

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.

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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.

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PATHOPHYSIOLOGY:

The Chromosomes


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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.")

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

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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.


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This is what a normal set of

chromosomes looks like.Note the 22 evenly paired

chromosomes plus the sex

chromosomes.

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.

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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

chromosomes.

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.

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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.

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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

chromosome.

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."

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CLINICALMANIFESTATIONS

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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:


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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

adolescence

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:

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Nursing Management:

1. Assess for associated problems.

2. Administer medications which maybe prescribed for associated

problems.

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.

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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:

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An amniocentesesis the prenatal procedure to diagnose

Down Syndrome. A chromosome test can be done after

birth.

Diagnosis

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

sampling.

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Treatment

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.

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Finally,children with DS may also benefit from occupational

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

strength, and coordination.

THE END

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