Fragile X syndrome: Difference between revisions

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== [[Fragile X syndrome causes|Causes]] ==
== [[Fragile X syndrome causes|Causes]] ==
Fragile x Syndrome is a genetic disease which is caused by mutation in the Fragile x Mental Retardation 1(FMR1) gene in X chromosome. Generally, these mutation (>200 repeats of CGG) occurs at in the 5' untranslated region of FMR1.<ref name="pmid22017584">{{cite journal| author=Santoro MR, Bray SM, Warren ST| title=Molecular mechanisms of fragile X syndrome: a twenty-year perspective. | journal=Annu Rev Pathol | year= 2012 | volume= 7 | issue=  | pages= 219-45 | pmid=22017584 | doi=10.1146/annurev-pathol-011811-132457 | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=22017584  }} </ref> In around 2% of cases, Fragile X syndrome can occur as a result of point mutation in FMR1 gene.<ref name="pmid22188182">{{cite journal| author=Peprah E| title=Fragile X syndrome: the FMR1 CGG repeat distribution among world populations. | journal=Ann Hum Genet | year= 2012 | volume= 76 | issue= 2 | pages= 178-91 | pmid=22188182 | doi=10.1111/j.1469-1809.2011.00694.x | pmc=3288311 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=22188182  }} </ref>


== [[Fragile X syndrome differential diagnosis|Differentiating Fragile X syndrome from other Diseases]] ==
== [[Fragile X syndrome differential diagnosis|Differentiating Fragile X syndrome from other Diseases]] ==

Revision as of 18:43, 2 September 2021

For patient information click here

Fragile X syndrome
Location of FMR1 gene
ICD-10 Q99.2
ICD-9 759.83
OMIM 309550
DiseasesDB 4973
MeSH D005600

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Synonyms and keywords:: Martin-bell syndrome; marker X syndrome, escalante's syndrome

Overview

Historical Perspective

Classification

Pathophysiology

Causes

Differentiating Fragile X syndrome from other Diseases

Fragile X syndrome must be differentiated from Autism Spectrum Disorder, Attention deficit hyperactivity disorder (ADHD), Fragile XE syndrome (FRAXE), Klinefelter syndrome and Prader-Willi syndrome (PWS).[1]

Epidemiology and Demographics

The prevalence of Fragile X syndrome is approximately 1 in 5000 men and 1 in 4000-6000 women worldwide, determined by molecular assays. [2] Fragile X Syndrome has been diagnosed in approximately 3 percent of boys with significant neurodevelopmental disorders. [3]

Risk Factors

There are no established risk factors for Fragile X syndrome. However, the child with family history of Fragile x Syndrome, autism disorder of unknown cause, developmental delay, adult onset ataxia/tremor or any intellectual disabilities are at greater risk of developing the disorder. [4]

Screening

Genetic counseling and prenatal screening is recommended when one of the parents is shown to be a carrier of fragile X. Prenatal testing can be done by amniocentesis at 16-20 weeks or by chorionic villus sampling (CVS) at 10-13 weeks to determine if a fetus has inherited the fragile X gene. [5]

Natural History, Complications and Prognosis

Diagnosis

The diagnosis of Fragile X Syndrome is based upon detection of an alteration in the fragile X mental retardation 1 (FMR1) gene. [6]

History and Symptoms

The physical features of Fragile X syndrome is prominent around the time of puberty. Physical features include:[7]

  • Large and protruding ears
  • Elongated face
  • Macroorchidism (large testicles in men after puberty)
  • Flat foot
  • High Arched palate
  • Hyperflexible finger joints
  • Low muscle tone

The common features in child with Fragile X Syndrome include low IQ with learning difficulties (intellectual disabilities). Behavioral abnormalities includes stereotypic movements (e.g., hand-flapping) hyperactivity, inattention, poor social interaction, limited eye contact and poor memory. Child with Fragile X syndrome often presents with developmental delay (including delayed attainment of motor and language milestones).[8] Approximately, 20% of boy with Fragile X syndrome develops seizures (mostly simple or complex partial seizures)[9]

Physical Examination

Laboratory findings

Other diagnostic studies

Treatment

Medical Therapy | Primary Prevention | Secondary Prevention | Cost Effectiveness of Therapy | Future or Investigational Therapies

Case Studies

Case #1


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  1. Wiesner GL, Cassidy SB, Grimes SJ, Matthews AL, Acheson LS (2004). "Clinical consult: developmental delay/fragile X syndrome". Prim Care. 31 (3): 621–5, x. doi:10.1016/j.pop.2004.04.008. PMID 15331251.
  2. Coffee B, Keith K, Albizua I, Malone T, Mowrey J, Sherman SL; et al. (2009). "Incidence of fragile X syndrome by newborn screening for methylated FMR1 DNA". Am J Hum Genet. 85 (4): 503–14. doi:10.1016/j.ajhg.2009.09.007. PMC 2756550. PMID 19804849.
  3. McConkie-Rosell A, Finucane B, Cronister A, Abrams L, Bennett RL, Pettersen BJ (2005). "Genetic counseling for fragile x syndrome: updated recommendations of the national society of genetic counselors". J Genet Couns. 14 (4): 249–70. doi:10.1007/s10897-005-4802-x. PMID 16047089.
  4. 1. Carrier Testing for Fragile X Syndrome [Internet]. ucsfhealth.org. [cited 2021 Jul 15]. Available from: https://www.ucsfhealth.org/Education/Carrier Testing for Fragile X Syndrome
  5. Mak AS, Leung KY (2017). "Challenges in prenatal screening and counselling for fragile X syndrome". Hong Kong Med J. 23 (2): 108–9. doi:10.12809/hkmj175064. PMID 28387201.
  6. Ciaccio C, Fontana L, Milani D, Tabano S, Miozzo M, Esposito S (2017). "Fragile X syndrome: a review of clinical and molecular diagnoses". Ital J Pediatr. 43 (1): 39. doi:10.1186/s13052-017-0355-y. PMC 5395755. PMID 28420439.
  7. McLennan Y, Polussa J, Tassone F, Hagerman R (2011). "Fragile x syndrome". Curr Genomics. 12 (3): 216–24. doi:10.2174/138920211795677886. PMC 3137006. PMID 22043169.
  8. Fisch GS, Simensen R, Tarleton J, Chalifoux M, Holden JJ, Carpenter N; et al. (1996). "Longitudinal study of cognitive abilities and adaptive behavior levels in fragile X males: a prospective multicenter analysis". Am J Med Genet. 64 (2): 356–61. doi:10.1002/(SICI)1096-8628(19960809)64:2<356::AID-AJMG24>3.0.CO;2-D. PMID 8844080.
  9. Hagerman PJ, Stafstrom CE (2009). "Origins of epilepsy in fragile X syndrome". Epilepsy Curr. 9 (4): 108–12. doi:10.1111/j.1535-7511.2009.01309.x. PMC 2728488. PMID 19693328.