fragile X syndrome

noun

variants or less commonly fragile X

: an X-linked inherited disorder that is characterized especially by moderate to severe intellectual and developmental disabilities, an elongated face and prominent forehead, chin, and ears, and by large testes in males, and that often has limited or no effect in heterozygous females

… most children with fragile X syndrome have other characteristic traits, including anxiety, hyperactivity, and a number of behaviors that are often seen in autism.

—Mark Cohen

The defective gene responsible for fragile X syndrome is carried on one leg of the X chromosome, the chromosome that helps determine the sex of a child.

—Elaine T. Cicora

Female carriers of fragile X syndrome as a group exhibit wide variation in degree of phenotypic involvement. Some heterozygotes are cognitively unaffected, others have learning disabilities, and approximately one third have significant mental impairment and an IQ score of less than 85.

—Annette K. Taylor et al.

Examples of fragile X syndrome in a Sentence

Recent Examples on the Web

Having 200 or more CGG repeats silences the FMR1 gene and results in fragile X syndrome. —Joel Richter, The Conversation, 26 July 2023

Beyond mice models Notably, fragile X syndrome is most often studied using mouse models. —Joel Richter, The Conversation, 26 July 2023

In the United States today, pregnant women can find out whether their unborn child has cystic fibrosis, fragile X syndrome, spinal muscular atrophy, or many other conditions. —Krithika Varagur, Harper's Magazine, 10 July 2023

But researchers have already delivered a gene for the protein missing in fragile X syndrome to mouse models of the condition. —Lydia Denworth, Science | AAAS, 14 Oct. 2020

Turner syndrome, fragile X syndrome, Prader-Willi syndrome, and other severe genetic disorders. —Jessie Balmert, The Enquirer, 2 Mar. 2021

The gene linked to fragile X syndrome lies on the X chromosome. —Emily Willingham, Discover Magazine, 18 Apr. 2019

Developing gene therapies for diseases that affect the central nervous system, including giant axonal neuropathy, Rett syndrome, and fragile X syndrome. —Ann Gehan, Dallas News, 2 Sep. 2021

Those with severe genetic disorders including Down syndrome, fragile X syndrome, Prader-Willi syndrome, Turner syndrome and muscular dystrophy. —Jessie Balmert, The Enquirer, 22 Mar. 2021

Word History

First Known Use

1979, in the meaning defined above

Medical Definition

fragile X syndrome

noun

-ˈeks- 

variants also fragile X

: an X-linked inherited disorder that is caused by repeats of a trinucleotide sequence on the X chromosome which are abnormal in number and degree of methylation, that is characterized especially by moderate to severe intellectual and developmental disabilities, an elongated face and prominent forehead, chin, and ears, and by enlarged testes in males, and that often has limited or no effect in heterozygous females

Female carriers of fragile X syndrome as a group exhibit wide variation in degree of phenotypic involvement. Some heterozygotes are cognitively unaffected, others have learning disabilities, and approximately one third have significant mental impairment and an IQ score of less than 85.

—Annette K. Taylor et al., The Journal of the American Medical Association

In approximately 10% of patients, autism can be explained by genetic syndromes and known chromosomal anomalies (most of which have recognizable features in addition to autism), including the fragile X syndrome, tuberous sclerosis, … and maternally inherited duplications of the region that is affected in the Prader-Willi and Angelman syndromes.

—Lauren A. Weiss et al., The New England Journal of Medicine