A condition characterized genotypically by mutation of the distal end of the long arm of the X chromosome (at gene loci FRAXA or FRAXE) and phenotypically by cognitive impairment, hyperactivity, SEIZURES, language delay, and enlargement of the ears, head, and testes. INTELLECTUAL DISABILITY occurs in nearly all males and roughly 50% of females with the full mutation of FRAXA. (From Menkes, Textbook of Child Neurology, 5th ed, p226)

A genetic syndrome caused by mutations in the FMR1 gene which is responsible for the expression of the fragile X mental retardation 1 protein. This protein participates in neural development. This syndrome is manifested with mental, emotional, behavioral, physical, and learning disabilities.

An X-linked dominant syndrome caused by expansion of the CGG triplets in the 5' promoter region of the FMR1 gene to over 200 copies. This expansion becomes hypermethylated, silencing the FMR1 gene expression, and subsequently completely inhibiting the expression of the fragile X mental retardation protein 1 (FMRP). The condition is characterized by a variety of developmental, emotional, behavioral, and physical symptoms, including learning disabilities and macroorchidism. Intermediate expansion of the CGG triplet (between 55 and 200 repeats) may be associated with a milder phenotype due to reduced expression of FMRP.

FMR1 disorders include fragile X syndrome (FXS), fragile X-associated tremor/ataxia syndrome (FXTAS), and fragile X-associated primary ovarian insufficiency (FXPOI). Fragile X syndrome occurs in individuals with an FMR1 full mutation or other loss-of-function variant and is nearly always characterized in affected males by developmental delay and intellectual disability along with a variety of behavioral issues. Autism spectrum disorder is present in 50%-70% of individuals with FXS. Affected males may have characteristic craniofacial features (which become more obvious with age) and medical problems including hypotonia, gastroesophageal reflux, strabismus, seizures, sleep disorders, joint laxity, pes planus, scoliosis, and recurrent otitis media. Adults may have mitral valve prolapse or aortic root dilatation. The physical and behavioral features seen in males with FXS have been reported in females heterozygous for the FMR1 full mutation, but with lower frequency and milder involvement. FXTAS occurs in individuals who have an FMR1 premutation and is characterized by late-onset, progressive cerebellar ataxia and intention tremor followed by cognitive impairment. Psychiatric disorders are common. Age of onset is typically between 60 and 65 years and is more common among males who are hemizygous for the premutation (40%) than among females who are heterozygous for the premutation (16%-20%). FXPOI, defined as hypergonadotropic hypogonadism before age 40 years, has been...

Fragile X syndrome is the most common form of inherited developmental disability. A problem with a specific gene causes the disease. Normally, the gene makes a protein you need for brain development. But the problem causes a person to make little or none of the protein. This causes the symptoms of Fragile X. People with only a small change in the gene might not show any signs of Fragile X. People with bigger changes can have severe symptoms. These might include Intelligence problems, ranging from learning disabilities to severe intellectual disabilities; Social and emotional problems, such as aggression in boys or shyness in girls; Speech and language problems, especially in boys. A genetic blood test can diagnose Fragile X. There is no cure. You can treat some symptoms with educational, behavioral, or physical therapy, and with medicines. Getting treatment early can help. NIH: National Institute of Child Health and Human Development

X-linked recessive disorder characterized by mental retardation and large head, jaw, ears, and testes; premutation alleles in unaffected carriers give rise to significantly amplified repeats in affected progeny.

Fragile X syndrome is a genetic abnormality on the X chromosome that leads to intellectual disability and behavioral disorders. Diagnosis is with molecular DNA analysis. Treatment is supportive.

Fragile X syndrome, also termed Martin-Bell syndrome or marker X syndrome, is the most common cause of inherited mental retardation, intellectual disability, and autism and is the second most common cause of genetically associated mental deficiencies after trisomy 21. In 1943, Martin and Bell investigated a family with multiple male...

Fragile X syndrome is a genetic condition involving changes in part of the X chromosome. This condition causes a range of developmental problems including learning disabilities and cognitive impairment. It is the most common form of inherited intellectual disability in males and a significant cause of intellectual disability in females....

Fragile-X syndrome, a chromosomal disorder associated with a fragile site on the end of the X chromosome. The major symptom of the syndrome is diminished mental ability, which may range from mild learning impairment to severe intellectual disability (or mental retardation). The X chromosome is one...