The Fragile X Syndrome is a genetic disorder involving the long arm of the X chromosome that results in developmental disability. Affected patients are usually male but women may also be affected.
Affected persons have an increased number of repeats for the trinucleotide sequence cytosine-guanine-guanine (CGG) in the FMR1 (Fragile X Mental Retardation 1) gene.
Patient Type
Number of CGG Repeats
normal
6 - 50
unaffected carriers with premutation
50 - 200
affected patients
> 200
Diagnostic testing includes cytogenetics and PCR amplification.
Indications for testing:
(1) any male or female with intellectual impairment, developmental delay or learning disabilities of unknown cause, no matter how subtle
(2) any male or female with autism or autistic-like characteristics
(3) a person with a family history of Fragile X syndrome
(4) a person with a family history of undiagnosed intellectual disability
(5) an individual with a previous Fragile X cytogenetic test that was inconclusive
(6) the fetus of a woman who is known to be a Fragile X carrier
(7) women with a family history of premature menopause
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