Fragile X Syndrome DNA Analysis by PCR, Blood
Test Mnemonic
FRAX
CPT Codes
- 81243 - QTY (1)
LOINC ®
36913-2
Aliases
- Carrier Screening
- FMR1
- Fragile X associated tremor ataxia syndrome
- FXTAS
- POI
- Primary ovarian insufficiency
Performing Laboratory
Cleveland Clinic Laboratories
Specimen Requirements
| Volume | Type | Container | Collect Temperature | Transport Temperature | Special Instructions |
|---|---|---|---|---|---|
| 4 mL | Blood | EDTA (Lavender) | Ambient | Ambient |
Minimum Specimen Requirements
| Volume | Type | Container | Collect Temperature | Transport Temperature | Special Instructions |
|---|---|---|---|---|---|
| 1 mL |
Stability
| Environmental Condition | Description |
|---|---|
| Ambient | 48 hours |
| Refrigerated | 7 days |
| Frozen | Unacceptable |
Days Performed
1 day per week
Turnaround Time
7 days
Methodology
| Name | Description |
|---|---|
| Capillary Electrophoresis (CE) | |
| Polymerase Chain Reaction (PCR) |
Reference Range
| Fragile X Report | |||||
|---|---|---|---|---|---|
| Sex | Age From | Age To | Type | Range | Range Unit |
| Freetext | Refer to Report |
Clinical Info
Fragile X syndrome (OMIM#300624) is the most common inherited cause of intellectual disability. In most cases, fragile X syndrome is caused by a trinucleotide (CGG) repeat expansion in the 5' untranslated (UTR) region of the FMR1 gene. Normally, there are fewer than 45 CGG triplet repeats but affected individuals have greater than 200 CGG repeats. These full mutations result in hypermethylation of the promoter region, with subsequest silencing of gene expression and absence of the FMR1 protein (FMRP). Alleles with 55 to 200 CGG repeats are considered premutations; they do not cause fragile X syndrome but are prone to meiotic instability and may expand to full mutations in one generation. 20% of women with premutations experience premature ovarian insufficiency (POI), with onset of menopause before the age of 40. Fragile X-associated tremor/ataxia syndrome (FXTAS), a late-onset neurodegenerative condition, has been identified as an FMR1-related disorder. FXTAS is seen predominantly in men, with onset after 50 years of age.