Fragile X (associated) Tremor/Ataxia Syndrome (FXTAS)

There may be a more appropriate test, please see: Fragile X Syndrome (FXS), Fragile X (associated) Primary Ovarian Insufficiency (FXPOI); Premature Ovarian Failure 1 (POF1)

Introduction

Fragile X associated Tremor/Ataxia Syndrome (FXTAS) is a late onset neurodegenerative disorder, whose major clinical manifestations include progressive intentional tremor, ataxia and Parkinsonism. The pathogenic mutation is an expansion (Premutation) in a CGG repeat tract of the FMR1 gene at Xq27.3, leading to increased transcription and a proposed toxic gain of function of FMR1 RNA.

Referral information

Testing is used for confirmation of a clinical diagnosis of FXTAS or for exclusion of the diagnosis in patients with relevant clinical indications. Within families with a history of FXTAS, testing is used to confirm a diagnosis or to establish or exclude carrier status following appropriate genetic counselling.

Technical information

Size analysis of the (CGG)n repeat region of the FMR1 gene is undertaken using PCR based technologies (Standard FMR1 PCR and/or AmplideX™ FMR1 PCR) see test validation details below.

Price & reporting times

NHS referrals to this service are paid for where there is an existing specialist commissioning contract for genetic testing. In other cases please contact the lab for prices.

Test Price (NHS)  

Price (non- NHS)

TRT (Calendar days)
Standard FMR1 PCR test/ AmplideX™ FMR1 PCR test POA POA 28

Test validation & quality assurance - information for users

The Standard FMR1 PCR test is used to detect “Normal” and “Intermediate” and some of the smaller “Premutation” alleles of the FMR1 CGG triplet repeat region. Larger “Premutation” and “Full Mutation” expansions cannot be detected with this method, and it is therefore used only as an “exclusion” test. If the Standard FMR1 PCR test results are inconclusive, the AmplideX™ FMR1 PCR test is performed (using a commercial kit, www.asuragen.com). This enables the detection of FMR1 repeat alleles up to and including full mutations (>200 repeats). Sizing accuracy for both tests is estimated to be +/-2 repeats for alleles in the Normal, Intermediate and Premutation ranges. The FMR1 PCR analysis has a sensitivity and specificity of >98%. The testing is therefore effective for exclusion of FXTAS as a likely diagnosis.

Sample requirements

4ml EDTA blood sample

Referral guidelines

Please see our referral guidelines for more information.

OMIM Number(s) - 300623

Gene(s) - FMR1

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