Fragile X Syndrome

Order dedicated FMR1 molecular testing for unexplained developmental delay, intellectual disability, autism-spectrum features, or a family history compatible with fragile X syndrome or another FMR1-related disorder. Males may have substantial developmental delay before recognizable physical features emerge; females may have milder developmental impairment. publications aappublications aapFragile X Syndrome (Chapter 253) | American Academy of Pediatrics Textbook of Pediatric Care | Pediatric Care Online | American Academy of Pediatrics

Do not use a negative routine multigene panel, exome, or genome result to exclude fragile X syndrome. These approaches are useful when no CGG-repeat expansion is detected but clinical suspicion persists, whereas FMR1 disorders require specialized molecular testing for the CGG expansion. PubMedPubMedFMR1 Disorders - GeneReviews® - NCBI Bookshelf

In an adult with intention tremor, gait ataxia, or a family history of FMR1 expansion, distinguish fragile X-associated tremor/ataxia syndrome from full-mutation fragile X syndrome by FMR1 repeat category. In a woman with ovarian insufficiency or reproductive counseling needs, determine whether a premutation is present because premutation status is associated with fragile X-associated primary ovarian insufficiency. PubMed+1PubMedFMR1 Disorders - GeneReviews® - NCBI Bookshelfpublications aapFragile X Syndrome (Chapter 253) | American Academy of Pediatrics Textbook of Pediatric Care | Pediatric Care Online | American Academy of Pediatrics

A definite molecular diagnosis of fragile X syndrome generally requires a full mutation exceeding 200 CGG repeats. These alleles are typically methylated, whereas premutation alleles of approximately 55-200 repeats are generally unmethylated. PubMedPubMedFMR1 Disorders - GeneReviews® - NCBI Bookshelf

Use an assay that can define expansion status and address methylation when a large expansion or mosaicism is possible. Repeat-primed PCR detects and localizes AGG interruptions; Southern blot detects normal alleles, larger premutations, and full mutations and determines FMR1 promoter methylation status. PubMedPubMedFMR1 Disorders - GeneReviews® - NCBI Bookshelf

Interpret phenotype by sex and molecular state. GeneReviews reports intellectual disability in essentially all males with a completely methylated full mutation and in about half of females with a full mutation; both repeat-size mosaicism and methylation mosaicism produce a broader functional range. PubMedPubMedFMR1 Disorders - GeneReviews® - NCBI Bookshelf

If targeted testing shows no CGG expansion but the patient remains clinically suspicious for a genetic neurodevelopmental disorder, proceed with broader genomic evaluation rather than relabeling the patient as having fragile X syndrome. PubMedPubMedFMR1 Disorders - GeneReviews® - NCBI Bookshelf

After DNA confirmation, arrange age-appropriate developmental and educational intervention rather than waiting for physical features to evolve. Early intervention can improve long-term cognitive outcomes, although it should not be presented as restoring normal cognitive outcome. Nature+1NatureMain Report | Genetics in Medicinepublications aapHealth Supervision for Children With Fragile X Syndrome

At follow-up, actively identify impairment from ADHD symptoms, anxiety, aggression, and sleep problems because these are recognized medication targets in fragile X syndrome. Select medication according to the dominant treatable syndrome and reassess functional benefit and adverse effects rather than treating the molecular diagnosis itself. WileyWileyState‐of‐the‐art therapies for fragile X syndrome

Assess for seizures when episodes suggest altered awareness, motor events, or unexplained regression. ADHD and epilepsy may coexist in fragile X syndrome; stimulant therapy and antiseizure treatment can be managed independently when both disorders are present. Oxford Academic+1Oxford Academic58 Attention-Deficit Disorders and Epilepsy - Oxford AcademicWileyDescriptive analysis of seizures and comorbidities ...

Use a multidisciplinary model that links the primary clinician, developmental and behavioral services, school supports, and genetics. The AAP health-supervision guidance is specifically designed for pediatric management after DNA confirmation. publications aappublications aapHealth Supervision for Children With Fragile X Syndrome

Counsel families that fragile X syndrome results from CGG-repeat hyperexpansion in the 5′ untranslated region of FMR1, which leads to promoter hypermethylation and loss of the encoded protein in full-mutation disease. PubMed+1PubMedFMR1 CGG repeat expansion mutation detection and linked haplotype analysis for reliable and accurate preimplantation genetic diagnosis of fragile X syndrome - PMCPubMedFMR1 premutation and full mutation molecular mechanisms ...

For a woman with a premutation, explain that the allele may expand to a full mutation during maternal transmission. Repeat length and AGG interruptions influence expansion behavior; expansion from premutation to full mutation has been documented in one generation, including a 59-repeat allele lacking AGG interruptions in a pedigree analysis. PubMed+1PubMedFMR1 CGG repeat expansion mutation detection and linked haplotype analysis for reliable and accurate preimplantation genetic diagnosis of fragile X syndrome - PMCPubMedExpansion of the Fragile X CGG Repeat in Females with Premutation or Intermediate Alleles - PMC

Offer targeted testing and counseling to biologically relevant relatives after identifying a full mutation or premutation. This can identify relatives at risk for fragile X syndrome, fragile X-associated tremor/ataxia syndrome, or fragile X-associated primary ovarian insufficiency and can inform reproductive planning. publications aap+2publications aapFragile X Syndrome (Chapter 253) | American Academy of Pediatrics Textbook of Pediatric Care | Pediatric Care Online | American Academy of PediatricsPubMedFMR1 Disorders - GeneReviews® - NCBI BookshelfCDCHow Fragile X Syndrome Is Inherited | Fragile X Syndrome (FXS) | CDC

When reproductive options are being considered, refer to reproductive genetics. Preimplantation genetic testing has used FMR1 PCR-based approaches, but large GC-rich premutation and full-mutation alleles can be difficult to amplify; linked-marker approaches may be needed to reduce misclassification risk. PubMedPubMedFMR1 CGG repeat expansion mutation detection and linked haplotype analysis for reliable and accurate preimplantation genetic diagnosis of fragile X syndrome - PMC