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Diagnostic Services

Genetics Lab


Fragile X

FMR-1 related disorders include fragile X syndrome, FMR-1-related premature ovarian failure (POF), and fragile X-associated tremor/ataxia (FXTAS). These disorders are due to a repetitive sequence of DNA (CGG repeat) that leads to an expansion of the FMR-1 gene. A normal FMR-1 gene has 5-40 CGG repeats. 59-200 repeats are considered premutations and >200 CGG repeats is a full mutation and causes fragile X syndrome. An estimated 1 in 4000 males are affected with fragile X syndrome. Features include developmental delay, learning disabilities, attention deficit, speech delay, gross and fine motor delay, and autistic like behavior. Many females are unaffected carriers of the full expansion, however, females can exhibit symptoms as well. Female carriers of a premutation can have FMR-1 related premature ovarian failure. Male premutation carriers can develop FXTAS, characterized by white matter lesions on MRI causing intention tremor or gait ataxia.

A second gene, FMR-2, also known as Fragile X E, is a rare cause of x-linked mental retardation. Greater than 200 GCC repeats is a full mutation and causes Fragile X E syndrome.

Test Name: Fragile X (A & E)
Test Code:
Test Description:
Molecular (DNA) testing to determine the number of CGG repeats in the FMR-1 gene and the number of GCC repeats in the FMR-2 gene.
Fragile X DNA analysis, FRAXA, FRAXE, FXTAS, POF
The test is indicated for:
1. Evaluation of male and female patients with mental retardation, developmental delay and autism.
2. Evaluation of women with premature ovarian failure.
3. Evaluation of older adult males with gait ataxia or intention tremor.
4. Carrier testing for women in a family with history of fragile X syndrome or undiagnosed mental retardation.
Related Tests:
Clinical Links: Fragile X Syndrome GeneReview
Fragile X E OMIM listing
Turnaround Time:
2-3 weeks
PCR; some samples require a Southern blot
Reference Range:
Interpretive report is provided.
Consent Form:
Sample Requirements: Type
1-3 mL whole blood in EDTA (purple top) or ACD (yellow top); DNA: 25ug extracted DNA (minimum concentration 100 ug/mL)

Do not spin. Refrigerate blood samples which will not be immediately shipped.

Transport at room temperature via overnight shipping.
Samples Received:
Mon-Fri 8 am - 5 pm PST
Special Considerations:
Fragile X (E) is bundled with this test. CPT codes below reflect both tests.
Please e-mail Lab Client Services ( or call at 206-987-2617 with any billing questions
CPT Code:
Please e-mail Lab Client Services ( or call at 206-987-2617 with any billing questions