Molecular Genetics Laboratory Services

Fragile X Syndrome

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About the Disorder | Indications | Specimen l Testing Methodology l Sensitivity l Turnaround Time l Cost l CPT Codes l Shipping l Results l Contact Us

About the Disorder

Fragile X syndrome is the most common inherited cause of mental retardation. It affects predominantly males but females may show autistic features, learning disabilities, or mental retardation. Increases in the number of CGG repeats in the Fragile X gene (FMR1) result in decreasing functionality of the FMR1 protein. Repeat size greater than 200 in males is associated with Fragile X syndrome. Females with repeat sizes of 56 up to 200 are considered pre-mutation carriers as they are at risk for passing on an expanded Fragile X gene with more than 200 repeats. Premutation carriers in both males and females have been described with learning difficulties, behavioral problems, and even mental retardation. Older males with premutations may develop neurologic symptoms such as tremors and ataxia (abnormal gait) called the Fragile X Tremor Ataxia Syndrome (FXTAS). FXTAS is a late-onset, progressive disorder affecting cognition and behavior. Females with premutations are at some risk for FXTAS-type symptoms but are at a higher than expected risk for developing premature ovarian failure.

Indications

Mental retardation or developmental delay of unknown etiology predominantly in males
Family history of Fragile X syndrome or nonspecific mental retardation
Features of autism in either males or females
Women with premature menopause
Tremor or ataxia in males over 50 with known family history of Fragile X

Specimen

At least 2ml of whole blood in purple top (EDTA) tube. Label tube with patient's name, birth date, and date of collection. Phlebotomist must initial tube to verify patient's identity.

Testing Methodology

DNA extracted from peripheral white blood cells is analyzed by the polymerase chain reaction (PCR). The PCR fragment is designed to flank the area of repeats and effectively alters the size of the PCR product correspondingly to the repeat size. The DNA is also subjected to Southern blot hybridization to analyze for fragments containing greater than 200 repeats (i.e. full mutations).

Sensitivity

Full mutations of the Fragile X gene (FMR1) are associated with Fragile X syndrome in >99% of cases.

Turnaround Time

2 weeks

Cost

Please call 866-450-4198 for current pricing.

CPT Codes

88390, 83892, 83894, 83898, 83896

Shipping Instructions

Please enclose test requisition with sample. All information must be completed before sample can be processed. Place samples in Styrofoam mailer and ship at room temperature by overnight Federal Express to arrive Monday through Friday.