FMR1 CGG Repeat Expansion Analysis

Clinical Use

Use

The FMR1 CGG Repeat Expansion Analysis determines the number of CGG repeats in the FMR1 gene, vital in diagnosing Fragile X syndrome (FXS), an X-linked disorder presenting as intellectual disability, distinctive facial features, and behavioral issues. Affected individuals typically exhibit over 200 CGG repeats, while premutation carriers have 55-200, facing risks for further conditions like FXTAS and FXPOI. FXS can cause cognitive deficits alongside physical traits, with a significant percentage of males and females at risk for associated syndromes. The analysis aids in genetic counseling, guiding reproductive decisions, and monitoring risk for future generations.

Special Instructions

This test should be considered for individuals with suspected FXS or family history. In addition to standard clinical relevance, carrier screening may be applicable for those planning a pregnancy, with special attention to the repeat count and its implications for the patient and their family. Testing may include further analysis if precursor stages are found.

Limitations

This assay may miss some patients affected by Fragile X syndrome, particularly those without more than 200 CGG repeats. For such individuals, deletion/duplication and sequence analysis of FMR1 gene may be warranted to ensure accurate diagnosis. The presence of AGG triplets can affect repeat stability but isn't routinely included in testing. Limitations also include constrained detection rates for certain subpopulations, necessitating comprehensive clinical correlation when interpreting results.

Test Details

New York Approved