From the Guidelines
Screening for Fragile X syndrome is necessary for an infant who is a child of a Fragile X carrier, and genetic testing, specifically a DNA test for Fragile X syndrome, should be considered. The American College of Medical Genetics, the American Academy of Neurology (AAN), and the American Academy of Pediatrics (AAP) recommend that all individuals with intellectual disability (ID) of undetermined etiology have specific testing for Fragile X syndrome 1. This is because Fragile X syndrome is a common cause of inherited intellectual disability and can have significant implications for the child's development and quality of life.
The testing process typically involves a simple blood sample, and results are usually available within a few weeks. Parents should consult with a genetic counselor before and after testing to fully understand the implications of the results and to discuss appropriate follow-up care if needed. Early diagnosis allows for prompt intervention services such as speech therapy, occupational therapy, and educational support, which can significantly improve outcomes.
Some key points to consider when screening for Fragile X syndrome include:
- The degree of intellectual disability/developmental delay does not predict the diagnostic yield of genetic testing 1
- FMR1 testing for Fragile X syndrome has a combined yield of at least 2% in male and female subjects with mild GDD/ID/IDD 1
- Early screening is important because Fragile X syndrome can cause developmental delays, intellectual disability, behavioral issues, and physical characteristics that may not be apparent in infancy
- The American College of Medical Genetics, the AAN, and the AAP recommend a chromosomal microarray in all individuals with ID of undetermined etiology, which may also help identify other genetic causes of intellectual disability 1
From the Research
Screening for Fragile X Syndrome
- The American Academy of Pediatrics recommends testing individuals with intellectual disability, global developmental retardation, or a family history of the mutation or premutation 2.
- Identifying fragile X syndrome at a young age can be challenging, but considering genetic testing for all males with unexplained developmental delays, intellectual disability, and autism, as well as females with developmental delays, intellectual disability, or autism, and a family history of fragile X gene disorders is crucial 3.
- Screening for fragile X syndrome is performed by polymerase chain reaction, and current recommendations suggest testing individuals with a family history of the mutation or premutation 2.
Carrier Screening
- The possibility of newborn screening for fragile X syndrome is complicated by the potential for identifying premutation carriers, which can have implications for the child's future health and reproductive decisions 4, 5.
- Knowing the child's carrier status has potential benefits, but the possibility of late-onset disorders in carrier children and their parents raises concerns about whether such information would be distressing to parents and potentially more harmful than helpful 5.
- A study found that disclosing newborn carrier status to parents did not result in significant adverse events, but greater spousal support was generally associated with more positive outcomes 5.
Recommendations for Infants of Fragile X Carriers
- Infants who are children of fragile X carriers may benefit from screening, as early identification and intervention can help maximize the child's learning potential 3.
- Genetic counseling is essential for families with a history of fragile X syndrome, as it can aid in future reproductive decisions and the risk of future recurrences of this condition 3.