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Fragile X Syndrome

Test performed by: LabPLUS - Dept. Diagnostic Genetics - Molecular Genetics

Referral Criteria for Fragile X testing

Clinical features characteristic of Fragile X syndrome or other FMR1 -related disorders.

Important Note

Diagnostic referral <15yrs through a Specialist Service.

Diagnostic referral >15yrs requires referral through Neurology, Psychiatry or Genetic Services.

All predictive/carrier only through Genetic Services.

Premature ovarian failure referrals can be accepted through Obstetrics.

LabPlus does NOT perform Fragile X analysis for preconception carrier testing unless there is a proven family history or the patient has clinical features consistent with a diagnosis of Fragile X syndrome.


Genetic Health Service NZ can be contacted on 0800 476 123.

Neurology can be contacted on (09) 307 4949 ext. 25662.


Microarray (Molecular Karyotype) Lab Test Guide

Download: : - LabPLUS GHSNZ Genetic Testing Pathway for DD ID MCA ASD.jpg

Download: : - LabPLUS Genetic Testing Criteria for Neonates.jpg

Specimen Collection
EDTA4 mL Paediatric EDTA Blood (Preferred)


For paediatric samples a minimum of 0.5ml blood EDTA can be processed. (Microcollect)

Transport all bloods at room temperature within 24-48 hours. If necessary specimens can be refrigerated overnight for transport at room temperature the following day.

For testing of other sample types please contact the laboratory prior to sending.

EDTA8 mL Adult EDTA Blood
Turnaround Time: Within 6 weeks
Contact Information

Mark Greenslade (Consultant Clinical Scientist): ext. 24330

Pippa Grainger (Scientist Unit Manager): ext. 22010

Molecular Genetics Team: ext. 22014

Background Information

Fragile X syndrome occurs in individuals with an FMR1 full mutation and is characterized by moderate mental retardation in affected males and mild mental retardation in affected females. Males may have a characteristic appearance (large head, long face, prominent forehead and chin, protuding ears), connective tissue findings (joint laxity), and large testes (postpubertally). Behavioral abnormalities, sometimes including autism spectrum disorder, are common.
The fragile X-associated tremor/ataxia syndrome (FXTAS) occurs in males who have an FMR1 premutation and is characterized by late-onset, progressive cerebellar ataxia and intention tremor. FMR1-related premature ovarian failure occurs in approximately 20% of females who have an FMR1 premutation.
More than 99% of individuals with fragile X syndrome have a full mutation in the FMR1 gene caused by an increased number of CGG trinucleotide repeats (>200 typically) accompanied by aberrant methylation of the FMR1 gene. Other mutations within FMR1 that cause fragile X syndrome include deletions, point mutations that disrupt RNA splicing, and a missense mutation. All individuals with FXTAS and all females with FMR1-related POF have an FMR1 premutation (increased number of trinucleotide repeats ranging from 55 to ~200).

For general information on the Molecular Genetics service

Molecular Genetics Information Page

Last updated at 11:43:46 13/10/2021