Chromosomal Disorders Nursing Lecture Resource

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Definitions
Gene: smallest unit of a single characteristic
Chromosome: structural elements in the cell nucleus that carry the genes and convey genetic information
Each cell (except RBO) contain all of the chromosomes from both parents in the nucleus
23 pairs of chromosomes come from each parent
Autosome: one of the 22 pairs of chromosomes that is not responsible for determining the sex of the child
Sex Chromosome: X and Y chromosomes responsible for sex determination

Chromosomal Defects
Abnormal Number
Monosomy: one less than the diploid number (45)
Trisomy: one more than the diploid number (47)
Mosaicism: some cells have the correct number of chromosomes and some have more or less than the correct number of chromosomes
Abnormal Structure
Deletion: loss of a chromosomal segment
Translocation: the occurrence of a chromosomal segment at an abnormal site either on another chromosome or in the wrong position on the same chromosome

Prenatal Diagnosis
Maternal Serum Alpha-fetoprotein (MSAFP)
Done at 16 – 18 wks gestation
High MSAFP: incorrect dates; multiple gestation; neural tube defects, abdominal wall defects; renal anomalies; esophageal or intestinal obstructions
Low MSAFP: incorrect dates; chromosomal defect (esp. Trisomy 21)
Ultrasound

Amniocentesis
Usually done at 16 – 18 wks gestation
Fluid analysis may require up to 2-3 wks
Can usually determine: fetal sex, metabolic disorders, chromosomal abnormalities
Chorionic Villus Sampling (CVS)
Usually done at 8 – 10 wks gestation
Fetal cell analysis usually takes 24 – 48 hours

Newborn Care
History
Family History: any similar relatives, frequency of spontaneous abortions
Prenatal History: fetal activity, maternal exposures, uterine malformations

Newborn Assessment
Face: configuration, spacing of feature, location of features
Head: size and shape of skull, fontanel
Eyes: structure, location, color of iris
Ears: low set or correct location, skin tags
Nose: number of nares, location, flattened bridge
Oral: size and shape of tongue, mouth, jaw
Neck: webbing, extra folds
Hands & Feet: broad, square, polydactyly, abnormal creasures, contractures, overriding fingers or toes

Family Support
Crisis
Grief – loss of “perfect child”
Genetic counseling
Identify the normal

Trisomy 21
a.k.a. Down’s Syndrome
Caused by an extra chromosome 21
Normal Karyotype Trisomy 21 ( 47,XY,+21)

Trisomy 21
Incidence
1 : 650 – 1000 live births, parental age related
75 % abort spontaneously
Sex ratio: 3 males / 2 females
Most common autosomal chromosomal disorder causing mental retardation
Risk Factors
maternal age
Parental carrier of translocation
Prenatal Testing
Triple screen (alpha-fetal protein decreased, estriol decreased, beta-HCG increased)
If positive, amnio or CVS may be indicated

Clinical Presentation
Size: small, 20% are premature
Skull: short and round with a flat occiput, separated sutures
Eyes: slant upward and outward
Prominent epicanthal fold
Moon-shaped face
Brushfield’s spots
Cheeks: red
Palate: narrow and short
Nose: short with flat bridge
Tongue: protrudes, tongue thrusting
Skin loose around lateral and dorsal aspects of neck
Hands: fingers are short, hands are square, thumbs are low set, separated more than usual from second finger, 5 th finger is short and curves inward, single/bilateral simean crease
Ears: low-set, posteriorly rotated ears

Umbilicus: herniated
Feet: wide space between great toe and 2 nd toe, deep crease between great toe and the 2 nd toe, flat feet
Heart: VSD
Duodenal atresia
Muscular hypotonia
Retarded psychomotor development
Hyperlaxity of ligaments
Velvety, loose adhering mottled skin in infancy, coarse skin in adolescence
Mouth frequently open/frequently open mouth
Visual and/or hearing impairment

Prognosis
Congestive heart failure d/t CHD
Upper respiratory tract infections
Developmentally delayed
Mildly to severely mentally retarded: IQ ranges from 25 – 70
Increased risk for thyroid problems and leukemia

Trisomy 18
a.k.a. Edward’s Syndrome, Trisomy E, Trisomy 16 – 18
Normal Karyotype Edward’s Syndrome (47,XY, +18)

Trisomy 18
Incidence
1 : 6000 – 8000 live births
F > M (4 : 1)
Most die in embryonic or fetal life
Risk factors
Increased paternal and maternal age
Prenatal screening
Good indicator is if in maternal serum during mid trimester have low human chorionic gonadotrophin and low unconjugated estriol
Ultrasound
If anomalies seen, amnio or CVS may be indicated

3 Types of Trisomy 18
Full Form
Every cell in the body has 3 chromosome 18 instead of 2
Severe form
Mosaic Form
Some cells have 3 chromosome 18 and others have 2
Less severe form
Partial Form
In some cells there may be an extra copy of part of chromosome 18
Severity dependent on anomalies

Prenatal hx: feeble fetal activity, polyhydramnios, small placenta, single umbilical artery
Post-dates
SGA
Weight: low birth weight in term infant
Weak cry
Response to sound decreased
Ears: low set and/or abnormal shape
Mouth: micrognathia, microstomia, cleft lip, cleft palate
Mental retardation
Heart: VSD, PDA, ASD
Feet: rocker bottom, big toe shortened and dorsiflexed, clubfeet
Crossed legs
Diastasis recti
Pectus carinatum
GU defects: horseshoe kidneys, hydronephrosis, polycystic kidneys

Hands: clenched and with flexed fingers (usually where index finger overlaps 3 rd and 4 th fingers),flexion contraction of the two middle digits, underdeveloped or absent thumb, simian crease, arches on seven or more fingers, nails underdeveloped
Syndactyly
Eyes: ptosis of one or both eyelids, epicanthal folds
Head: abnormally prominent occiput, microcephaly
Hernias: umbilical, inguinal
Redundant skin folds esp. over the back of the neck
Males: cryptorchidism

Prognosis
20 – 30% die during the first month
90% die by age one
1% chance of surviving to 10 yrs
High mortality rate is caused by congenital heart malformations, gastrointestinal and genitourinary anomalies, feeding difficulties, and associated central nervous system defects that produce central apnea.
Although they function with severe handicaps, all older children with Trisomy 18 smile, laugh, interact, relate to their families, and achieve some psychomotor maturation.
Mosaic cases may show milder phenotypic expression and prolonged survival.

Care Management
No treatment beyond supportive care
NG or GT feedings
Orthopedic management
Cardiac management
Genetic counseling
Parental support
Apnea monitoring / O 2 if needed

Trisomy 13
a.k.a. Patau’s Syndrome, 13+ Syndrome, 13 – 15 D Syndrome, Trisomy Syndrome
Normal Karyotype Trisomy 13 (47,XX,+13)

Trisomy 13
Incidence
1 : 5000 live births
Male = Female
Risk Factors
Increases with maternal and paternal age
Increases with increased parity
Parental carrier of balanced translocation
Prenatal Screening
Ultrasound
If anomalies seen, amnio or CVS may be indicated

Severe mental and psychomotor retardation
Ears: malformed, low-set
Hands: flexion deformities; polydactyly, simian crease, clenched hands
Heart: VSD, PDA, ASD, rotational anomalies (dextrocardia)
Eyes: microphthalmos, colobomas of iris, cataracts, retinal dysplasia, close set (may fuse into one)
Nose: broad and flattened
Mouth: cleft lip and palate
Hernias: umbilical hernia, inguinal hernia
Kidneys: polycystic
Skin: cutaneous hemangiomas
Head: dermal sinus on scalp, microcephaly
Brain: gross defects, grand mal seizures, myoclonic jerks, seizures, holoprosencephaly

Skin loose around lateral and dorsal aspects of neck
Single umbilical artery
Apnea
Genitalia
Female: bicornate/septate uterus
Male: cryptorchidism
Mouth: cleft lip, cleft palate
Spine: meningomyelocele
Feet: rocker bottom
Low-birth weight
Omphalocele
GI XR or US may reveal abnormal rotation of internal organs

Prognosis
82% die within the first month
5 - 10% survive the first year
Survival to adulthood rare
Common disorders if survive beyond 1 month of age
Severe mental retardation
Feeding disabilities
GE reflux
Slow post natal growth
Apnea
Kidney defects
Seizures
Developmental disabilities
Scoliosis

Care Management
No treatment beyond supportive care
Parental support

Turner’s Syndrome
a.k.a. TS, Monosomy X, Gonadal Dysgenesis, Bonnevie-Ullrich Syndrome, XO Syndrome
Is the absence of one set of genes from the short arm of one X chromosome
Normal Karyotype Turner’s Syndrome (45,X)

Turner’s Syndrome
Incidence
1 : 2000-3000 live-born females
Females only affected
98% of pregnancies with TS spontaneously abort
10% of pregnancies that spontaneously abort have TS
Risk Factors
Increased paternal age
Mother with mosaic or deletional Turner’s Syndrome
SHOX gene association
SHOX gene provides instructions for making a protein that regulates activity of other genes

Short stature; mean birth weight 2.9 kg; average height: 4’7”
Webbed neck
Low posterior hairline
Micrognathia
Ears: low-set, sometimes malformed, prone to otitis media
Widely spaced hypoplastic nipples on a shield-shaped chest
Increased carrying angle at the elbow
Heart: coarctation of the aorta, aortic vavular stenosis, bicuspid aortic valve, aortic dissection
Eye: ptosis, strabismus, amblyopia, cataracts, epicanthal folds, dry eyes, red-green color blindness
Congenital hip dislocation
Abnormal growth patterns
Congenital lymphedema of hands and feet

Absent or retarded development of secondary sexual characteristics that normally appear at puberty
Absent menstruation
Absence of normal vaginal moisture
infertility
Gonadal dysplasia
Horseshoe kidney
Unilateral renal agenesis
Intelligence: not at risk for mental retardation, better verbal then visuospatial abilities
Broad nasal bridge

Prognosis
Females are basically normal despite failure of sexual development
At risk for
Middle ear infections
Scoliosis
Arthritis
Cataracts
Hashimoto’s thyroiditis
Kidney abnormalities
High blood pressure
Obesity
Diabetes mellitus
Osteoporosis
Keloid formation

Care Management
Early
Supportive care
Surgery to correct treatable defects
Late
Growth hormone therapy
Estrogen replacement therapy
Counseling and psychiatric support
2 – 5% have some ovarian function and can menstruate and become pregnant
Others can have children using donor eggs and in-vitro fertilization

VATER Association
VATER = V ertebral anomalies
A nal atresia
T racheo- E sophageal fistula,
R adial and renal dysplasia
Incidence
Unknown
Etiology
Unknown

Three or more of the following defects must be present:
Vertebral anomalies
Anal atresia with or without fistula
TEF with EA
Radial dysplasia, including thumb or radial hypoplasia, polydactyly, and syndactyly
Renal anomaly
Single umbilical artery

Prognosis
FTT
Possibility of normal life after slow mental development during infancy
Care Management
Supportive care
Surgery: surgical correction of anomalies

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Chromosomal Disorders Nursing Lecture Resource

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