Genetic Syndromes - CTE - Online Learning Management System

Genetic Syndromes
Chromosomes
Sex Linked Syndromes
Gene Defects
Development of Young Children with Disabilities
#872.514 (61)
Carol Ann Heath
CHROMOSOMAL
ABNORMALITIES
What is a Trisomy?
A chromosomal anomaly characterized by
the presence of an extra chromosome in
the cells
A trisomy occurs when there are 47
chromosomes instead of 46
A partial trisomy occurs when just part of
an extra chromosome attaches to another
Trisomy continued
Mosaic trisomy occurs when the extra
chromosome material is not present in every
cell
The most common known trisomies are:
Trisomy 21 (Down syndrome)
Trisomy 18 (Edward’s syndrome)
Trisomy 13 (Patau’s syndrome)
Trisomy 21: Down syndrome
Extra 21st chromosome; 47 chromosomes
in each cell
1/800 births
Approximately 5,000 children with Down
syndrome born each year in U.S.
1% chance of reoccurrence
Life expectancy: approximately 55 years
Down syndrome
96% of children with Down syndrome
have the extra chromosome 21
4% have either a translocation (attached
to or incorporated into another
chromosome in the egg or sperm) or a
form called “Mosaic” in which not all cells
affected.
Mosaic children may be less delayed
Prevalence
Prevalence increases with maternal age:
29 years and younger
30-34 years
35-39 years
40-44 years
over 45 years
1/1500
1/800
1/270
1/100
1/50
Physical Characteristics
Hypotonia
short neck
oval-shaped eyes
(excess skin)
epicanthal folds
single palmar creases
small nose
flattened nasal bridge
small oral cavity
small ears that may fold slightly at top
Health problems associated
with Down syndrome
40-50% have congenital heart defects
Respiratory problems, especially upper
respiratory infections
Eye and ear problems including hearing loss
Thyroid problems
Cervical spine abnormalities
Gastrointestinal problems
Down syndrome continued
Most have some degree of mental retardation
ranging from mild to severe.
Average person functions in mild to moderate
range.
Education in public schools
Perform daily living skills independently
Can marry and have children (rare for men)
Women have 50% their child will have DS
Development
Better prognosis due to:
better health care
early intervention
more normal family and social
experiences
better educational opportunities
more positive social attitudes
Development continued
Social and emotional development in
infancy delayed, they progress in the first
year is essentially normal.
Hypotonia delays motor skills which
restricts their early experiences.
Visual exploration and eye-contact
delayed in first year.
Development continued
Expressive language skills delayed
May be able to sign words before
verbalizing them
3/4 children have speech production
problems
4/5 may experience some degree of
hearing loss (fluctuating caused by o.m.)
Development continued
Many children have auditory-perceptual
impairment (tree/cheese)
At risk for dyspraxia-inability to perform
coordinated movements
Benefits of sign language
A way of teaching speech and language
Method of communicating and expression
Develop comprehension of speech
Assisting with Language
Sign language
computers
open/closed questions
role play
synthesized speech
Reading
Most early reading books contain too little
text and text that is too complex
Reading single words first:
matching
selecting
naming
Trisomy 13
Sometimes referred to as Patau Syndrome
Described in 1657, etiology not
discovered until 1960 by Dr. Klaus Patau
Extra 13th chromosome which results in
significant multiple defects in major organ
systems
Brain most severely affected
Many born blind, deaf, no sense of smell
Trisomy 13
1/8000 births
Median survival is 2.5 days
82% die within the first month
5% survive first 6 months
Those surviving longer have severe
mental defects, seizures, and failure to
thrive
Only 1 adult known to survive to age 33
Abnormalities
80% heart defect
60-80% cleft lip, cleft palate or both
Found in 50% or more patients:
central nervous system
hearing
cranium
eyes
skin
hands and feet
skeletal
genitalia
Etiology
Maternal age has been a factor with
occurrence
Chance of recurrence is thought to be low
Trisomy 13 mosaicism usually show a less
severe clinical phenotype, survival may be
longer, and mental deficiency variable
Trisomy 18
Also known as Edward’s syndrome
Discovered in 1960 by Dr. John Edwards
Caused by an extra 18th chromosome
It is the second most common multiple
malformation syndrome
1/6,600 births
Affects females 3:1
Trisomy 18
50% die within first week
Only 5-10% survive the first year as
“severely mentally defective individuals”
10 children over the age of 10 reported
Most unable to walk and language limited,
but some older children who survive may
interact and relate to family members.
Abnormalities
Growth deficiency
congenital anomalies of the heart, lung,
kidneys, and diaphragm
increased muscle tone
small mouth and jaw
mental deficiency
microcephaly
Abnormalities continued
Low set malformed ears
small pelvis, limited hip abduction
underdeveloped nails
underdeveloped or absent thumbs
abnormal genitalia
episcanthal folds
Etiology
Maternal age contributing factor to
occurrence
1% chance of recurrence
Moscaicism leads to partial clinical
expression, longer survival and various
degrees of variations
Sex Linked
Abnormality in the overall number of
chromosomes for X and Y
Male has one X and One Y
Female has two X
Disorders
Turner syndrome: female abnormality
Female has only one X, total of 45, not 46
chromosomes, resulting in XO pattern
Only case in which too few chromosomes
can develop into an embryo and survive
1/5000 female births
Turners
Very short <5 ft
Lowered hairline, broad chest and short
neck
Ovaries do not function normally
IQ in typical range with learning
disabilities, particularly visual-perceptual
and mathematics
Klinefelter syndrome
Males has extra X chromosome, resulting
in 47
Pattern of XXY
1/500 males
Taller and thinner; underdeveloped
secondary sex traits; decreased hormone
level
Language delays; normal adulthood
Chromosome deletions
Sometimes genetic material is missing from a
chromosome. These chromosomes are said to
have “deletions”.
Interstitial deletions occur when a chromosome
has broken, genetic material has been lost, and
the chromosome arms rejoin
Larger deletions lead to death
Chromosomal Errors
Deletion #22q11.2 syndrome
Williams syndrome
Fragile X
Cri du chat
Cri du chat syndrome
First described in 1963 by Lejeune
Syndrome associated with deletion of the
short arm of chromosome5
Deletion can vary in size from extremely
small (involving only one band) to the
entire short arm
Majority of children die in early childhood,
some survive into adulthood with low IQ
Prevalence
One of the most common deletion
syndromes
Varying between 1/20,000 and 1/50,000
Abnormalities
Low birth weight
Slow growth
cat-like cry
hypotonia
mental deficiency
microcephaly
strabismus
72%
100%
100%
78%
100%
100%
61%
Abnormalities continued
Round face
epicanthal folds
Low set and/or poorly
formed ears
congenital heart disease
68%
85%
57%
30%
Development
As babies, unusually squirmy
Cat-like cry that becomes less prominent with
age
With special schooling and supportive home
environment, some children have attained social
and psychomotor skills of a 5 to 6 year old
50% had vocabulary adequate for
communication
William syndrome
Described in 1961 by Williams
deletion of one allele located within
chromosome subunit 7q11.23
1/20,000 births
Abnormalities
Mild growth deficiency
mild microcephaly
small upturned nose
long philtrum
epicanthal folds
cardiac anomalies
joint limitations
Performance
Average IQ is 56 (range 40-80)
Hoarse voice
Hypersensitive to sound
Mild neurologic dysfunction
Poor coordination
Decreased perceptual and motor function
Language ability much greater than cognitive
ability
Development
Infancy: feeding problems, colicky, fretful
Childhood: outgoing, no fear of
strangers, strong interest in others
2/3 of children: difficult temperament,
more negative moods, increased activity,
distractible, less persistence, and low
threshold arousal
Development continued
As adults: progressive medical problems
Most live with parents or in group home
Sudden death reported in a number of
children
Deletion #22q11.2
syndrome
Previously known as DiGeorge syndrome
1 out 5000 births
Common cause of genetic heart malformation
Facial anomalities: small mouth, narrow eyes,
bulbous nose, palate
Immune deficiency
Typical cognitive ranges with learning
disabilities, particularly in math
Fragile X Syndrome
Mental Impairment
Females:
learning disabled in math
exceptional with reading and spelling
1/3 have mental disabilities similar to those
associated with schizophrenia
Males:
process information in simultaneous fashion
Sees whole in order to understand the parts
Speech and Language
Rapid bursts
Echolalic
Perseveration most difficulty for males
Talking inappropriately
One topic
Speech problems made worse if anxious
Behavioral Problems
ADHD
Temper tantrums
Mood swings
Aggression
Strong reaction to change in environment
Sensory integration
Autistic like behaviors
Medical Problems
At greater risk for otitis media
Myopia
“Lazy eye”
Orthopedic difficulties related to flat feet
and joint laxity
20% of males prone to seizures
Digestive disorders
Education
Early Intervention
Mainstreaming
Occupational therapy
Speech therapy
Physical therapy
Visual devices
Fragile X
Identified by a break or weakness on the
long arm of the X chromosome
FMR-1
X linked
“Genetic anticipation”
Testing for Fragile X
Fragile X syndrome
Most Common Genetically inherited form
of mental retardation
1991 clinical method of diagnosing
Occurs in 1/1000 male births
Occurs in 1/2500 female births
Life span is normal
Physical Characteristics
Long narrow face
Large or prominent ears
Macroorchidism
Abnormalities of connective tissue:
double jointed fingers
Flat feet
Heart Murmur
Mental Impairment
80% of males have mental impairment
ranging from severe retardation to lownormal intelligence
Majority: mildly to moderately retarded
30% of females have some degree of
mental retardation
IQ appears to decline with age
Mental Impairment cont.
Common learning disabilities include
delayed speech
attention problems
hyperactivity
math
Good with imitation
Very social
Visual Memory
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