Reference Interval:
By report
|
| Interpretive Data: |
Fragile X (FMR1) Diagnostic
Characteristics: Fragile X syndrome, the most common heritable form of mental retardation, is characterized by moderate mental retardation in males and mild mental retardation in females, hyperactivity, perseverative speech, social anxiety, poor eye contact, hand flapping or biting, autism spectrum disorders behavioral phenotype, and connective tissue anomalies. Adult males may have physical findings including: macroorchidism, a long narrow face, prominent ears and jaw, and a single palmar crease.
Incidence: 1 in 4,000 Caucasian males and 1 in 8,000 Caucasian females; unknown in other ethnicities
Inheritance: X-linked dominant.
Penetrance: Reduced in females.
Cause: Expansion of the FMR1 gene CGG triplet repeat.
Full mutation: >200-230 CGG repeats (methylated)
Premutation: 55-200 CGG repeats (unmethylated)
Intermediate: 45-54 CGG repeats (unmethylated)
Normal: 5-44 CGG repeats (unmethylated)
Clinical Sensitivity: 99 percent.
Methodology: PCR and Southern blot hybridization. Methylation analysis is performed to distinguish between premutation and full mutation alleles. The sex chromosome gene amelogenin is used to confirm gender but also may indicate the possibility of X chromosome aneuploidies such as Klinefelter or Turner syndrome.
Analytic Sensitivity and Specificity: 99 percent
Limitations: Analytic sensitivity may be compromised by PCR primer site mutations.
Counseling and informed consent are recommended for genetic testing. Consent forms are available online at www.aruplab.com.
Refer to Statement C under Testing Information at http://www.aruplab.com.
| Phenotype
| Number of CGG Repeats
| | Unaffected
| < 45
| | Intermediate
| 45-54
| | Premutation
| 55-200
| | Affected
| >200
|
|
| CPT Code(s): |
PCR: 83891 Isolation; 83898 x2 Amplification; 83909 Capillary electrophoresis Southern Blot: 83891 Isolation; 83892 x2 Digestion; 83894 Gel Separation; 83897 Southern transfer; 83896 Nucleic acid probe; 83912 Interpretation & report - Additional CPT code modifiers may be required for procedures performed to test for oncologic or inherited disorders.
|
Cross References: |
Inherited Mental Retardation (Fragile X (FMR1) Diagnostic)
, Martin-Bell Syndrome (Fragile X (FMR1) Diagnostic)
|
|
![[ image for: Patient History For Molecular Genetic Testing]](icon_21.jpg){kind=icon}