Back متلازمة الصبغي X الهش Arabic Martin-Bell sindromu Azerbaijani Síndrome X fràgil Catalan Fragiles-X-Syndrom German Σύνδρομο ευθραύστου χρωμοτοσώματος X Greek Fragila X sindromo Esperanto Síndrome X frágil Spanish X hauskorraren sindrome Basque سندرم ایکس شکننده Persian Fragile-X-oireyhtymä Finnish

Fragile X syndrome

Fragile X syndrome
Other namesMartin–Bell syndrome,[1]
Escalante syndrome
Boy with protruding ears characteristic of fragile X syndrome
SpecialtyMedical genetics, pediatrics, psychiatry
SymptomsIntellectual disability, long and narrow face, large ears, flexible fingers, large testicles[1]
ComplicationsSeizures[1]
Usual onsetNoticeable by age 2[1]
DurationLifelong[2]
CausesGenetic (X-linked dominant)
Diagnostic methodGenetic testing[2]
TreatmentSupportive care, early interventions[2]
Frequency1 in 4,000 (males), 1 in 8,000 (females)[1]

Fragile X syndrome (FXS) is a genetic neurodevelopmental disorder characterized by mild-to-moderate intellectual disability.[1] The average IQ in males with FXS is under 55, while about two thirds of affected females are intellectually disabled.[3][4] Physical features may include a long and narrow face, large ears, flexible fingers, and large testicles.[1] About a third of those affected have features of autism such as problems with social interactions and delayed speech.[1] Hyperactivity is common, and seizures occur in about 10%.[1] Males are usually more affected than females.[1]

This disorder and finding of fragile X syndrome has an X-linked dominant inheritance.[5] It is typically caused by an expansion of the CGG triplet repeat within the FMR1 (fragile X messenger ribonucleoprotein 1) gene on the X chromosome.[1] This results in silencing (methylation) of this part of the gene and a deficiency of the resultant protein (FMRP), which is required for the normal development of connections between neurons.[1] Diagnosis requires genetic testing to determine the number of CGG repeats in the FMR1 gene.[6] Normally, there are between 5 and 40 repeats; fragile X syndrome occurs with more than 200.[1] A premutation is said to be present when the gene has between 55 and 200 repeats; females with a premutation have an increased risk of having an affected child.[1] Testing for premutation carriers may allow for genetic counseling.[6]

There is no cure.[2] Early intervention is recommended, as it provides the most opportunity for developing a full range of skills.[7] These interventions may include special education, speech therapy, physical therapy, or behavioral therapy.[2][8] Medications may be used to treat associated seizures, mood problems, aggressive behavior, or ADHD.[9] Fragile X syndrome tends to show more symptoms on affected males since females have another X chromosome which can compensate for the damaged one.[4][10]

  1. ^ a b c d e f g h i j k l m n "fragile X syndrome". Genetics Home Reference. April 2012. Archived from the original on 9 October 2016. Retrieved 7 October 2016.
  2. ^ a b c d e "What is Fragile X Syndrome?". National Center on Birth Defects and Developmental Disabilities. US: Centers for Disease Control and Prevention. 3 June 2022. Archived from the original on 10 May 2017. Retrieved 10 May 2017.
  3. ^ Raspa M, Wheeler AC, Riley C (June 2017). "Public Health Literature Review of Fragile X Syndrome". Pediatrics. 139 (Suppl 3): S153–S171. doi:10.1542/peds.2016-1159C. PMC 5621610. PMID 28814537.
  4. ^ a b "Data and Statistics Fragile X Syndrome (FXS)". Centers for Disease Control and Prevention. 2018-08-09. Archived from the original on 2019-10-13. Retrieved 2018-11-05.
  5. ^ Friedman JM, Howard-Peebles PN (1986). "Inheritance of fragile X syndrome: an hypothesis". American Journal of Medical Genetics. pp. 701–713. doi:10.1002/ajmg.1320230161. Retrieved 10 November 2024.
  6. ^ a b "Technical Standards and Guidelines for Fragile X". www.acmg.net. 2006. Archived from the original on 12 October 2016. Retrieved 10 May 2017.
  7. ^ "What are the treatments for Fragile X syndrome?". www.nichd.nih.gov. Archived from the original on 2016-11-21. Retrieved 2016-11-21.
  8. ^ "Therapy Treatments". NICHD. Archived from the original on 5 May 2017. Retrieved 10 May 2017.
  9. ^ "Medication Treatments". NICHD. Archived from the original on 5 May 2017. Retrieved 10 May 2017.
  10. ^ "What is Fragile-X syndrome?". @yourgenome · Science website. Retrieved 2023-07-15.

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