Fragile X Syndrome (cont.)
Physical
Many infants and young children with Fragile X have no distinctive physical
features. Some children have very soft, velvety skin, a broad forehead, or a
slightly larger head than other children their age.
However, when these children enter puberty, usually around age 11, they may
begin to develop certain features that are typical of teens and adults with
Fragile X, such as a longer face or jaw and larger, more noticeable ears. Most
do not grow as tall as their peers, or as tall as one might expect them to grow,
based on the height of their family members.
Other physical changes also come with puberty for those who have Fragile X.
Many males develop enlarged testicles, a condition called macro-orchidism
(pronounced mack-roe-ORK-id-izm). With this condition, the testicles may grow to
twice their normal size. This condition is not due to hormonal imbalance and
does not affect sexual development.
One job of FMRP may be to help the body maintain its connective tissues.
Connective tissues support the body, inside and out. Many people with Fragile X
have loose, flexible joints. They may have flat feet and be able to extend
joints like the thumb, knee, and elbow further than normal. Weak connective
tissue can predispose a person to certain medical conditions, such as hernia and
frequent middle ear infections. Weak connective tissue can also affect the
valves and vessels of the heart, so that blood in the heart may not flow
smoothly, which creates a heart murmur (called mitral valve prolapse, pronounced
my-trell valv proh lapss). Although it involves the heart, this condition is
usually not life threatening, but it is a good idea for a person with a heart
murmur to be monitored by a health care professional on a regular basis.
Late in life, some males who have a premutation may develop hand tremors10 and problems with walking.
| How does Fragile X affect the brain? |
| Understanding how Fragile X affects the brain and learning what role
FMRP plays in normal brain development and function are areas of active
research. For instance, some evidence suggests that FMRP is involved in
forming pathways in the brain.
Normally, brain cells called neurons have special areas that grow
toward each other to form connections. These connections, called
"synapses," are arranged in neural pathways. Thoughts, sounds, and
memories are recorded and stored in these pathways. However, not every
experience recorded in these neural pathways is useful or needs to be
kept throughout life. So, as part of normal development, the brain
"prunes" itself. Like pruning the branches of a tree, removing unneeded
or ineffective pathways in the brain strengthens other pathways and
makes room for new growth and new learning.
FMRP may somehow influence the pruning process in the brain. People
without enough FMRP may have may have too many neural pathways or many
connections that don't work well. This situation would explain some of
the symptoms of Fragile X, such as an extreme sensitivity to new sights,
sounds, smells, and touches.
Using mice and fruit flies that no longer have a working gene to make
FMRP, scientists are working to understand how the absence of this
protein affects the brain. Recent research is trying to determine
whether a certain process that runs out of control in mice with little
or no FMRP leads to the behavioral and learning problems typical in
people with Fragile X. Such animal studies may reveal exactly how FMRP
functions in the brain and suggest ways to correct situations caused by
a lack of the protein. |
Fragile X affects females in some different ways. About 16 percent11 to 19 percent12 of females who have a premutation gene experience premature ovarian failure (POF), meaning their ovarian function stops before normal menopause, sometimes well before the age of 40. Some may experience POF as early as their mid-twenties. POF affects a woman's ability to get pregnant. It is important, then, for women to know whether or not they have a premutation gene, and to have this knowledge early enough, so that they can consider their options for having a family. In contrast, POF occurs in only 1 percent of women who have two normal FMR1 genes,13
and the average age of menopause for women who are not affected by Fragile X is
51. Women who have a full mutation gene do not lose ovarian function as early as
women with a premutation gene, but they still tend to begin menopause earlier
than women who are not affected by Fragile X. Scientists do not know why the
effect is milder in women who have a full mutation form of the gene than in
women with a premutation form of the gene.
Next: Social and emotional »
- Amniocentesis - Learn about amniocentesis, a procedure that examines the chromosomes of the fetus to determine lung maturity, and the possiblities of birth defects.
- Learning Disabilities - Read about learning disabilities, like the skills affected such as reading, writing, listening, speaking, reasoning, and mathematics. Causes, symptoms, diagnosis, and treatment information is included.
- Premature Ovarian Failure (POF) - Learn about premature ovarian failure (POF) - (the normal functioning of ovaries in women under 40 stop). Some causes of POF include follicle depletion or dysfunction.
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