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Fragile X and Klinefelter Syndromes Fragile X and Klinefelter Syndromes
by Kimberly Allen, RN Fragile X Syndrome Fragile X syndrome or FXS is a genetic disorder affecting the X chromosome.  If affects both boys... Fragile X and Klinefelter Syndromes

by Kimberly Allen, RN

Fragile X Syndromefragile x

Fragile X syndrome or FXS is a genetic disorder affecting the X chromosome.  If affects both boys and girls, however, if affects boys almost twice as often as girls.  It is the most common cause of inherited mental retardation, autism and intellectual disability in boys.
FXS is a genetic disorder that is inherited from your parents.  Because FXS involves the X chromosome fathers can only pass the mutation on to their daughters.  FXS is a dominant genetic disorder meaning only one copy of the X chromosome needs to be affected for you to develop this disorder.  In FXS there is a mutation in a gene called the FMR1 gene.  This gene supplies the information needed to produce the FMRP known as the fragile X mental retardation protein.  The FMRP controls the production of other crucial proteins as well as assists in the development of the connections between your nerve cells known as synapses.  In almost all cases of FXS the mutation occurs in a segment of DNA called the CGG triple repeat.  This segment of DNA is normally  repeated anywhere from 5 to 40 times.  However, in people born with FXS the CGG segment is repeated from 55 to over 200 times.  The more repeats of the CGG segment you have the worse the condition.  This abnormally high repetition causes the CGG segment to prevent the FMR1 gene from producing FMRP.  Because FMRP is crucial to the development of your nervous system, when it is not produced causing a shortage there is a disruption in the function of your nervous system causing the symptoms related to FXS.
The symptoms of FXS varies depending on the number of repetitions of the CGG segment.  Also, because boys have only one X chromosome their symptoms tend to be more severe than girls.  Children born with FXS can manifest symptoms in numerous areas including development, cognitive and neuropsychological as well as musculoskeletal and recurrent health issues.  Some symptoms are noticeable after birth while others become more noticeable as your child gets older.  Most boys as well as around half the girls born with FXS have physical features that are characteristic of FXS like a long narrow face with a prominent jaw and forehead as well as large ears.  Boys with FXS tend to develop enlarged testicles after puberty.  There are also numerous development delays that occur in children born with FXS including delays in sitting, crawling and walking.  As your child gets older you’ll notice delays in your child’s speech and language development as well as impairment in their fine motor skills.  Children with FXS also tend to have behavioral problems that can range from ADHD to autism.  Also, approximately 15% of boys and approximately 5% of girls with FXS have seizures.
There is currently not cure for FXS nor is there a specific treatment.  However, there are education and training programs that can help your child to function and improve their quality of life.  Some of these services would include a speech and language therapist to help your child slow their speech and improve word pronunciation as well as to use language more effectively.  Physical and occupational therapists to help improve your child’s balance and posture.  They can also instruct parents on different ways of exercising their child’s muscles.  A behavioral intervention and modification therapist can help your child to understand and properly use social eye contact as well as stress management.
Early intervention is crucial.  The sooner your child starts receiving help for his/her FXS the better the outcome.  many of these services are available through the public school system to school aged children and are usually free.  If your child requires more intense and/or individualized assistance you can find these services in private clinics, however, most insurance companies don’t cover the cost so you may have to pay for the services.

Klinefelter Syndromeklinefelter syndrome

Klinefelter syndrome is also called the XXY condition and it affects only males.  It is a genetic condition in which boys are born with an extra X chromosome.  Instead of the normal XY chromosomes they have one or more extra X chromosomes giving them the XXY.  Klinefelter syndrome is considered fairly common and the incidence has been increasing over the past 10 years.  Most experts believe that at least 1 out of every 500 boys born is born with at least 1 extra X chromosome.  Klinefelter syndrome affects males of all racial, ethnic and socio economic groups worldwide.
Although Klinefelter syndrome is a genetic condition it is not inherited from your parents.  It occurs due to a random, spontaneous mutation that causes a boy to be born with one or more extra X chromosomes.  The most common form of Klinefelter syndrome is the single extra X chromosome, XXY chromosomes in most cells in the body.  A boy can also be born with and extra X chromosome in some of their cells while the others have the normal XY chromosome.  This type of Klinefelter syndrome is called mosaic Klinefelter syndrome.  There is also a rare and more severe form of Klinefelter syndrome that is the result of a boy being born with more than one extra X chromosome.
In many cases boys born with Klinefelter syndrome have either no symptoms or they are not noticeable and frequently go undiagnosed until adulthood.  However, for some boys born with Klinefelter syndrome they experience noticeable symptoms that significantly affect their growth and development.  They also tend to have learning and speech disabilities.  The severity of symptoms depends on how many cells have the mutated XXY chromosomes.  Boys born with noticeable Klinefelter syndrome usually have weak muscles along with decreased strength.  This causes a delay in his when he meets certain developmental milestones like sitting, crawling and walking.  They also tend to learn to speak later than other boys.  As many as 85% of boys born with Klinefelter syndrome have difficulty not only with learning to speak but using language to express themselves.  The also have difficulty with reading and processing what they hear.  These babies are usually quiet and less demanding than other boys,  Then as they get older they’re usually more shy and quiet, they also tend to struggle in school as well as in sports making it more difficult for them to ‘fit in’ with other kids their age.
Boys  born with the XXY mutation are usually taller and don’t have as much muscle control and coordination as other boys their age.  As the boys with Klinefelter syndrome enter puberty they generally don’t produce as much testosterone as boys with the normal XY chromosome.  This usually leads to a body that is less muscular with less facial and body hair as well as broader hips then most boys.  As teenagers boys with Klinefelter syndrome have weaker bones and larger breasts as well as less energy than other teenage boys.  By the time boys born with Klinefelter syndrome reach adulthood they look similar in appearance as other men though they tend to be taller.
Though there is no way to change or repair the mutated chromosome associated with Klinefelter syndrome there are a variety of treatments available that can help you manage the condition and minimize the effects it has in your body.  These range from testosterone replacement therapy to assist a boy with Klinefelter syndrome through puberty to speech and physical therapy to assist in overcoming difficulties with speech and language as well as muscle weakness.  There are even fertility treatments available for men with Klinefelter syndrome as most men with this condition have no or very little sperm.
Most boys born with Klinefelter syndrome can lead normal productive lives with proper treatment and support.  Early detection and treatment improves your or your child’s ability to lead a productive life.

Kimberly Allen is a registered nurse with an AND in nursing. She has worked in ACF, LCF and psychiatric facilities, although she spent most of her career as a home health expert. She is now a regular contributor to, dispensing advice and knowledge about medical issues and questions. You can reach her with any comments or questions at