For predictive testing, it is important to first document the presence of CGG-repeat amplification in the FMR1 gene in an affected family member to confirm that molecular expansion is the underlying mechanism of disease in the family.
Test results should be interpreted in the context of clinical findings, family history, and other laboratory data. Errors in our interpretation of results may occur if information given is inaccurate or incomplete.
Methylation status will not be assessed on chorionic villus specimens nor will it be assessed if the reported gender is female.
Less than 1% of individuals clinically diagnosed with fragile X syndrome do not have the CGG expansion-type mutation. These individuals may have a different type of mutation within the FMR1 gene (eg, deletion or point mutation).
Due to incomplete penetrance and variable expression of the FMR1 expansion, this test is not reliable for prenatal assessment of disease severity.
The absence of an expansion in the FMR1 gene does not eliminate the diagnosis of other inherited disorders that have overlapping clinical features with fragile X syndrome, fragile X tremor/ataxia syndrome, or premature ovarian insufficiency.