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Fragile X syndrome

Synonyms
FRAGILE X MENTAL RETARDATION SYNDROME; Fra(X) syndrome; Fragile X syndrome, type A; MENTAL RETARDATION, X-LINKED, ASSOCIATED WITH marXq28; Marker X syndrome; Martin-Bell syndrome; X-linked mental retardation and macroorchidism
Modes of inheritance
X-linked dominant inheritance (Orphanet)

Summary

Excerpted from the GeneReview: FMR1 Disorders
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 observed in 20% of women who carry a premutation allele compared to 1% in the general population.
Full text of GeneReview (by section):
Summary
GeneReview Scope
Diagnosis
Clinical Characteristics
Genetically Related (Allelic) Disorders
Differential Diagnosis
Management
Genetic Counseling
Resources
Molecular Genetics
References
Chapter Notes
Authors:
Jessica Ezzell Hunter
Elizabeth Berry-Kravis
Heather Hipp
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Available tests

214 tests are in the database for this condition.

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Clinical tests (214 available)

Biochemical Genetics Tests

Molecular Genetics Tests

Genes See tests for all associated and related genes

  • Also known as: FMRP, FRAXA, POF, POF1, FMR1
    Summary: fragile X messenger ribonucleoprotein 1

Clinical features

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Imported from Human Phenotype Ontology (HPO)

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Reviews

Clinical resources

Practice guidelines

  • ACMG ACT, 2012
    American College of Medical Genetics and Genomics Genetic Testing ACT Sheet, Fragile X [FraX] Syndrome, 2012
  • EuroGenetest, 2011
    Clinical utility gene card for: fragile X mental retardation syndrome, fragile X-associated tremor/ataxia syndrome and fragile X-associated primary ovarian insufficiency.

Molecular resources

Consumer resources

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