Fragile X syndrome
Fragile X syndrome, also known as Martin-Bell syndrome, is a genetic disorder characterized by developmental disabilities and variable physical traits. It arises from a mutation in the FMR-1 gene located on the X chromosome and is inherited in a sex-linked manner, affecting boys more frequently and severely than girls. Common physical features associated with the syndrome include a long, thin face, prominent jaw and ears, and large hands with loose joints. Non-physical symptoms often manifest as intellectual disabilities, learning challenges, attention span issues, hyperactivity, and sometimes behaviors resembling autism.
While there is no cure for Fragile X syndrome, various treatments can help manage symptoms. Interventions may include medication for attention and hyperactivity, alongside supportive therapies in educational settings. Early intervention is critical, as studies suggest that cognitive abilities may decline over time in affected individuals. The syndrome was initially recognized in the late 1960s, with advances in genetic testing enabling more consistent diagnoses since the 1980s. Genetic counseling is recommended for families with a history of the condition to better understand its implications.
Fragile X syndrome
ALSO KNOWN AS: Martin-Bell syndrome
ANATOMY OR SYSTEM AFFECTED: Brain, ears, feet, genitals, hands, joints
DEFINITION: A genetic disorder of variable expression, with developmental disabilities being the most common feature.
CAUSES: Genetic
SYMPTOMS: Thin face, prominent jaw and ears, broad nose, large testicles in males, large hands with loose finger joints, severe intellectual disabilities or learning disabilities, unusual speech patterns, problems with attention span and hyperactivity, motor delays, occasional autistic-type behaviors
DURATION: Chronic
TREATMENTS: None; alleviation of symptoms
Causes and Symptoms
Fragile X syndrome is caused by a change in a gene located on the long arm of the X chromosome. It is a sex-linked inherited disease, transmitted from parent to child, with boys being affected much more often and more severely than girls. According to the Centers for Disease Control and Prevention (CDC) in 2022, approximately 1 in 7,000 males and 1 in 11,000 females worldwide.
While symptoms and their severity vary widely, common physical features of fragile X syndrome include a long, thin face, a prominent jaw and ears, a broad nose, a high palate, large testicles (macroorchidism) in males, and large hands with loose finger joints. Physical features are more subtle in females. Nonphysical features include a range of intellectual and learning disabilities, with the majority of affected males demonstrating a range from low-normal intelligence to severe intellectual disability. More recent research has found that the intelligence quotients (IQs) of males with fragile X syndrome appear to decline throughout childhood. Associated behavioral symptoms include unusual speech patterns, problems with attention span, hyperactivity, motor delays, and occasional autistic-type behaviors, such as poor eye contact, hand-biting, or hand-flapping.
Treatment and Therapy
While there is no cure for fragile X syndrome, a number of possible interventions can address various symptoms. Medications can be administered to assist with attention span and hyperactivity, as well as with aggressive behavior. Schools can provide children with assistance in speech, physical therapy, and vocational planning. Early childhood special education services for children prior to school age can provide necessary early intervention that may prove most helpful if indeed the rate of learning for children with fragile X syndrome slows with age. Genetic counseling is advised for families who carry the gene.
Perspective and Prospects
In 1969, the discovery was made of a break or fragile site on the long arm of the X chromosome. However, it was not until the 1980s that consistent diagnoses of fragile X syndrome were made. In 1991, the responsible gene was sequenced and named the FMR-1 gene. Cytogenetic and testing are available to identify affected persons.
Bibliography:
Alan, Rick, and Rimas Lukas. "Fragile X Syndrome." Health Library, Oct. 11, 2012.
"Fragile X Syndrome." MedlinePlus, 11 Mar. 2016, medlineplus.gov/fragilexsyndrome.html. Web. Accessed 1 Apr. 2024.
Hagerman, Randi Jensen, and Paul J. Henssen. Fragile X Syndrome: Diagnosis, Treatment, and Research. 3d ed. Baltimore: Johns Hopkins University Press, 2002.
Maxson, Linda, and Charles Daugherty. 3d ed. Genetics: A Human Perspective. Dubuque, Iowa: Wm. C. Brown, 1992.
Moore, Keith L., and T. V. N. Persaud. The Developing Human: Clinically Oriented Embryology. 9th ed. Philadelphia: Saunders/Elsevier, 2013.
National Fragile X Foundation. Fragile X–Associated Disorders (FXD). 3d ed. Walnut Creek, Calif.: National Fragile X Foundation, Sept. 2009.
Parker, James N., and Philip M. Parker, eds. The Official Parent’s Sourcebook on Fragile X Syndrome. Rev. ed. San Diego, Calif.: Icon Health, 2005.
Sherwood, Lauralee. Human Physiology: From Cells to Systems. 8th ed. Pacific Grove, Calif.: Brooks/Cole/Cengage Learning, 2013.
Webb, Jayne Dixon, ed. Children with Fragile X Syndrome: A Parents’ Guide. Bethesda, Md.: Woodbine House, 2000.
"What is Fragile X?" FRAXA Research Foundation, 2013.
"What Is Fragile X Syndrome?" Centers for Disease Control and Prevention, 3 June 2022, www.cdc.gov/ncbddd/fxs/facts.html. Web. Accessed 1 Apr. 2024.