Clinical Reference Systems: Pediatric Advisor 10.0
Fragile X Syndrome
Description
Fragile X syndrome is an inherited disorder caused by a
mutation (a change in the genetic information) of a specific
gene.
Fragile X syndrome can cause hyperactivity, learning
problems, and emotional problems. It can also cause mental
retardation, although some children with fragile X have
normal IQs. This disorder is the most common known cause of
inherited mental retardation.
Cause
Fragile X syndrome is a genetic disorder. The parents or
other family members did not do anything to cause it. The
gene mutation has usually been carried unknowingly for many
generations. Both males and female carriers can have a
small fragile X mutation (called a premutation) and still be
completely normal. The premutation can expand to a larger
full mutation when it is passed on to the next generation
through a female. It is the full mutation that causes
fragile X syndrome. Your child may be the first one in your
family with behavior or development problems, or there may
be other relatives who are affected by the fragile X
mutation. Your doctor or a genetic counselor will explain
how this gene mutation is passed on in your family and who
should be tested for it.
The characteristic problems of fragile X syndrome are caused
by the full mutation of a specific gene called the fragile X
mental retardation 1 gene (FMR1). Genes are the building
blocks of chromosomes. Each person has 23 pairs of
chromosomes. One pair, called the sex or X and Y
chromosomes, determine whether a person is male or female.
Females have two X chromosomes and males have one X and one
Y chromosome. In fragile X syndrome the gene mutation is on
an X chromosome.
The full mutation in the FMR1 gene causes the FMR1 gene to
turn off. Therefore, the normal message for building a
special protein from this gene is missing, and the lack of
this protein is the cause of the developmental and
behavioral problems in fragile X syndrome.
Usually boys are affected more severely than girls because
the FMR1 gene is on the X chromosome and boys have only one
X chromosome. Because a girl has two X chromosomes, her
second X chromosome usually does not contain the mutation
and therefore helps suppress the problems caused by the
mutation on the other X chromosome.
Physical, Behavioral, and Health Concerns
- Physical characteristics
Boys affected by fragile X syndrome often have prominent
ears, a large head, a prominent forehead, extra flexible
finger joints, a high palate, soft skin, and flat feet.
During puberty, boys usually develop large testicles
(called macroorchidism) and a somewhat long face. Many
of these features are seen in the general population so
most of these boys look normal even though they have
features of fragile X syndrome.
Girls may also have physical features associated with
fragile X syndrome, particularly large or prominent
ears, very flexible finger joints, and flat feet.
- Health concerns
In general, children with fragile X syndrome do not have
a lot of medical complications. The health problems
they may have include:
- frequent ear infections
- seizures (occur in about 20% of children with fragile
X)
- strabismus, which is a weak eye muscle and occurs in
about 30% of children with fragile X
- mitral valve prolapse, a heart valve problem, which
occurs in about 50% of adults with fragile X
- rarely, a hernia or joint dislocation.
- Behavioral characteristics
The major problems associated with fragile X syndrome
involve behavior and slow development leading to a lower
IQ. The majority of girls with fragile X syndrome show
learning problems and a short attention span along with
shyness, social anxiety, and moodiness. Approximately
30% of girls with fragile X syndrome are mentally
retarded. The majority of males with fragile X syndrome
are mentally retarded, meaning that their IQs are below
70.
Children with fragile X are usually extra sensitive to
stimuli in their environment, such as noises or changes
in their routine. They are usually anxious and have
frequent tantrums.
For most boys and some girls with fragile X, the
activity level is high and the attention span is short.
Language development is especially slow. Most boys do
not talk much by age 3. Unusual behaviors, sometimes
termed autisticlike behaviors, commonly develop by 3
years of age. Some of these behaviors are hand
flapping, hand biting, poor eye contact, excessive
chewing on clothes, and pulling away from touch. These
children may ask questions over and over again even
after hearing the answer.
- Strengths of children with fragile X
Children with fragile X syndrome have many strengths,
including their social abilities (although shyness is
common); a wonderful sense of humor; an excellent memory
for people, events, and directions; intense interests;
and outstanding imitation skills.
Treatment
There is no cure for fragile X syndrome, but many treatments
are available.
- Therapy
If your child is diagnosed in infancy, your doctor will
discuss infant stimulation programs. Developmental
preschool programs are helpful for children under 5
years.
Speech, language, occupational, and physical therapy are
important to optimize motor skills and language
development. A sensory integration type of occupational
therapy can be helpful for behavioral problems. The
occupational therapist will demonstrate physical calming
techniques, such as deep pressure back rubs and joint
compression, which may help to calm behavior outbursts
or tantrums at home.
Your doctor or psychologist can help you establish a
behavior program at home that includes consistent
structure, regular routines, and positive feedback.
- Education
Your child's special education program in school should
include participation in regular education whenever
possible, individualized help to modify assignments and
tutor weak academic areas, speech and language therapy,
occupational therapy, and computers. Your doctor can
help you obtain these services and appropriate therapy
when needed.
- Medical care and medications
Your doctor will treat the medical problems that may
occur in a child with fragile X syndrome.
Your doctor may prescribe medications that can improve
poor attention span, hyperactivity, tantrums,
aggression, anxiety, obsessive thinking, or other
behavioral or emotional difficulties. Medication may
work with other methods of treatment to improve your
child's learning and behavior. Your doctor will tell
you about the side effects of any medication that is
recommended. Such medications are used for a trial
period and are continued only if they are found to be
helpful. If your child has an adverse response to
medication, you should call your doctor and discuss the
response.
Genetic Tests
There are two types of blood tests for fragile X syndrome.
One is the chromosome, or cytogenetic, test, which can show
the break in the X chromosome. The second is a newer DNA
test that is more exact and less expensive.
Because fragile X syndrome is a genetic disorder, you should
consider this during future pregnancies. Prenatal diagnosis
and new reproductive technologies should be discussed with
your genetic counselor.
Parent Support Groups
When the diagnosis of fragile X syndrome is made for your
child, it is often helpful to talk to another family with a
child who is similarly affected. The National Fragile X
Foundation, at 1-800-688-8765 or (303) 333-6155, has a list
of resource centers and parent support groups. It is helpful
to call them directly for educational information and the
phone number of a parent nearest you.
Remember, children with fragile X syndrome are difficult to
raise, and parents need to have personal time and recovery
time on a regular basis. If you as parents feel
overwhelmed, depressed, or excessively anxious, discuss this
with your doctor. He or she can help you. When you as
parents are healthy, you can better help your child reach
his or her optimal potential.
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