Transcript Fragile x syndrome

FRAGILE X SYNDROME
BY JORDON NAGEL
WHAT IT LOOKS LIKE…
WHAT IS FRAGILE X SYNDROME?
• This is a genetic condition that causes a range of developmental problems including learning
disabilities and cognitive impairment. Usually males are more severely affected by this
disorder than females.
• Affected individuals usually have delayed development of speech and language by age 2.
• Seizures occur in about 15 percent of males and about 5 percent of females with this
disorder.
• Children with this disability may have anxiety and hyperactive behavior such as fidgeting or
impulsive actions.
• Most males and about half of females with fragile X syndrome have characteristic features
that become more apparent with age.
HOW COMMON IS FRAGILE X SYNDROME?
• Fragile X syndrome is the most common inherited cause of intellectual
disabilities and the most common known cause of autism.
• Fragile X syndrome occurs in approximately 1 in 4,000 males and 1 in 8,000
females.
• About 1 in 259 women carry fragile X and could pass it to their children.
• About 1 in 800 men carry Fragile X; their daughters will also be carriers.
• Large-scale population studies of Fragile X still need to be done, but it is
clear that this is one of the most common genetic diseases in humans.
Most people with Fragile X are not yet correctly diagnosed.
WHAT GENES ARE RELATED TO FRAGILE X
SYNDROME?
• Mutations in the FMR1 gene cause fragile X syndrome. The FMR1 gene provides instructions for making
a protein called fragile X mental retardation 1 protein, or FMRP.
•
This protein helps regulate the production of other proteins and plays a role in the development of
synapses, which are specialized connections between nerve cells.
• Nearly all cases of fragile X syndrome are caused by a mutation in which a DNA segment, known as the
CGG triplet repeat, is expanded within the FMR1 gene. Normally, this DNA segment is repeated from 5
to about 40 times.
•
In people with fragile X syndrome, however, the CGG segment is repeated more than 200 times. The
abnormally expanded CGG segment turns off (silences) the FMR1 gene, which prevents the gene from
producing FMRP.
• Loss or a shortage (deficiency) of this protein disrupts nervous system functions and leads to the signs
and symptoms of fragile X syndrome.
HOW DO PEOPLE INHERIT FRAGILE X SYNDROME?
• Fragile X syndrome is inherited in an X-linked dominant pattern. A condition is
considered X-linked if the mutated gene that causes the disorder is located on the X
chromosome, one of the two sex chromosomes.
• The inheritance is dominant if one copy of the altered gene in each cell is sufficient
to cause the condition. X-linked dominant means that in females (who have two X
chromosomes), a mutation in one of the two copies of a gene in each cell is sufficient
to cause the disorder.
• In males (who have only one X chromosome), a mutation in the only copy of a gene
in each cell causes the disorder. In most cases, males experience more severe
symptoms of the disorder than females.
FRAGILE X INHERITED
• Each child of a carrier woman has a 50% chance of inheriting the mutated gene.
• A mother who is a carrier of Fragile X has a 50% chance of passing the mutated gene on to
each of her children.
• Those children can in turn also be carriers or they might be fully affected with Fragile X
syndrome.
• Carrier men will pass the premutation to all their daughters but none of their sons.
• These daughters are carriers but they do not have Fragile X syndrome.
• The Fragile X premutation can be passed silently down through generations in a family before
a child is born with the syndrome.
HOW IS FRAGILE X SYNDROME TREATED?
• There is no specific treatment available for fragile X syndrome. Supportive
therapy for children who have fragile X syndrome includes:
• Special education and anticipatory management including avoidance of
excessive stimulation to decrease behavioral problems.
• Medication to manage behavioral issues, although no specific medication has
been shown to be beneficial.
• Early intervention, special education and vocational training.
• Vision, hearing, connective tissue problems, and heart problems when
present are treated in the usual manner.
WHAT IS THE LIFE EXPECTANCY OF SOMEONE WHO
HAS FRAGILE X SYNDROME?
• Most people who have Fragile X Syndrome are
perfectly healthy in the aspect of life expectancy.
• Their life expectancy is no different than a normal
person.
WHAT KIND OF RESTRICTIONS ARE THERE FOR PEOPLE
WHO HAVE FRAGILE X SYNDROME?
• The symptoms of Fragile X Syndrome and their severity vary widely amongst those who have the
condition.
• Some with Fragile X Syndrome will face little or no difficulty with many kinds of physical work. In
most cases, the mental impairments associated with Fragile X Syndrome won’t have much effect
on your ability to perform physical tasks.
• For those with more severe symptoms, the other demands of physical work, especially if it involves
working around other people in a typical work environment, cannot reasonably be met.
• Those with moderate to severe symptoms of Fragile X Syndrome will generally not be expected to
be capable of performing sedentary labor. Most sedentary jobs require a great deal of attention to
detail, whether dealing with paperwork or with the public. Often, these jobs also require a high
degree of manual dexterity, which is often a problem for people with Fragile X Syndrome.
CAN YOU PREVENT FRAGILE X SYNDROME?
• Fragile X syndrome is a genetic condition, so it cannot be
prevented.
• However, people with fragile X in their families can undergo
genetic testing to see if they carry the gene mutation and
therefore have the possibility of passing it on to their children.
• Although fragile X syndrome cannot be prevented, early
intervention usually helps people with this condition achieve their
highest potential in terms of cognition, behavior, and more.
WHAT OTHER NAMES DO PEOPLE USE FOR FRAGILE X
SYNDROME?
FRAXA Syndrome
Fra(X) Syndrome
FXS
Marker X Syndrome
Martin-Bell Syndrome
X-linked mental retardation and macroorchidism
WORKS CITED
• http://ghr.nlm.nih.gov/condition/fragile-x-syndrome
• http://www.fraxa.org/fragilex/cause/
• http://www.nichd.nih.gov/health/topics/fragilex/conditio
ninfo/Pages/treatments.aspx