Fragile X Syndrome by Anjana Suresh

Fragile X Syndrome is an extremely common cause of intellectual disability in both males and females.

In 1943, scientists Martin and Bell showed that a particular form of mental retardation (later known as fragile X syndrome) was X-linked, meaning that the gene causing this trait was located on the X chromosome. In 1969, Herbert Lubs developed the chromosomal test for Fragile X. The test was not used extensively until the late 1970's. In 1991,the FMR1 gene that causes Fragile X was identified and was documented as fragile x syndrome.

Most cases of Fragile X are caused by a mutation in the FMR1 gene. A DNA segment known as the CGG triplet repeat is repeated more than 200 times in people with this syndrome, inactivating the FMR1 gene. This prevents the gene from producing the fragile X mental retardation protein, leading to symptoms and signs of Fragile X. Both boys and girls can be affected, but since boys have only one X chromosome, Fragile X is likely to affect boys more severely.

Fragile X Syndrome affects 1 in 4000 males and 1 in 8000 females worldwide and about 1 in 151 females and 1 in 468 males in the United States. It is not limited to a specific racial or ethnic group and can affect anyone.

A boy who has fragile X syndrome will have moderate intellectual disability. They have a different facial appearance with a large head size and forehead, a long face, chin and protruding ears. Males who have fragile X syndrome also have loose joints. Affected boys may have behavioral problems such as hyperactivity, hand flapping, hand biting, temper tantrums and autism. After boys have reached puberty, symptoms can include poor eye contact, problems in impulse control and distractibility. Physical problems that have been seen include eye, orthopedic, heart and skin problems. Girls who have the full FMR1 mutation have more mild forms of intellectual disability.

Family members who have fewer repeats in the FMR1 gene (the CGG codon) may not have intellectual disability, but may have other problems. Women with less severe changes may have premature menopause or difficulty becoming pregnant. Both men and women may have problems with tremors and can express poor coordination.

It is hard to diagnose fragile X in babies, but some signs include a larger head circumference, and differences in facial characteristics. In females, intellectual disability may be the only sign of the problem. A specific genetic test (polymerase chain reaction [PCR]) can be used to diagnose fragile X syndrome. This test looks for an expanded mutation called a triplet repeat in the FMR1 gene.

There is no specific treatment available for fragile X syndrome, but there is supportive therapy for children with fragile x syndrome. Examples of supportive therapy include special education, early intervention, and vocational training. Although many children diagnosed with fragile X syndrome have learning and behavioral problems, they can generally live normal life spans and don’t develop major medical problems.

Fragile X is inherited in an X-linked dominant pattern, meaning that the gene associated with the disease is located on the x chromosome.

Medical and psychological assessments for family members of people diagnosed with Fragile X Syndrome are being conducted. The study focuses on identifying areas of specific deficits and how the disease is inherited. This study hopes to find new ways to accurately measure brain changes in some carriers of the fragile X gene.

Works Cited:

Anatomic Abnormalities. 2013. Pediatrics Clerkship, The University of Chicago, www.pedclerk.bsd.uchicago.edu. Accessed 4 Feb. 2017.

“Fragile X Prevalence.” National Fragile X Foundation, 2017, www.fragilex.org. Accessed 4 Feb. 2017.

“Fragile X Research and Treatment Center.” UC Davis Mind Institute, UC Regents, 2017, www.ucdmc.ucdavis.edu. Accessed 4 Feb. 2017.

“Fragile X Syndrome.” Counsyl, 2017, www.counsyl.com. Accessed 4 Feb. 2017.

Fragile X Syndrome. 2014. Genetics 4 Medics, www.genetics4medics.com. Accessed 4 Feb. 2017.

Fragile X Syndrome. 2013. Pediatrics Clerkship, The University of Chicago, www.pedclerk.bsd.uchicago.edu. Accessed 4 Feb. 2017.

An illustration showing the appearance of normal and Fragile-X chromosomes. 2017. Your Genome, www.yourgenome.org. Accessed 4 Feb. 2017.

“Learning About Fragile X Syndrome.” National Human Genome Research Institute, National Institutes of Health, 27 June 2016, www.genome.gov. Accessed 4 Feb. 2017.

“Standard Protein BLAST.” BLAST, National Center for Biotechnology Information, 2017, www.blast.ncbi.nlm.nih.gov/. Accessed 4 Feb. 2017.

“What is Fragile X?” Friends for Fragile X, 2010, www.friendsforfragilex.org. Accessed 2 Feb. 2017.

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