CPT® Code 81172

AFF2 (ALF transcription elongation factor 2 [FMR2]) (eg, fragile X intellectual disability 2 [FRAXE]) gene analysis; characterization of alleles (eg, expanded size and methylation status)

The CPT® Code 81172 pertains to the molecular genetic testing of the AFF2 gene, which is also known as the AF4/FMR2 family, member 2 (FMR2) gene. This testing is specifically designed to characterize alleles associated with fragile X intellectual disability 2 (FRAXE). The procedure involves analyzing the gene for mutations that can lead to various developmental and cognitive challenges, including developmental delays, autism spectrum disorder (ASD), intellectual disabilities, learning difficulties, communication deficits, attention problems, and hyperactivity. The AFF2 gene is situated on the long arm of the X chromosome at position Xq28 and plays a crucial role in the regulation of mRNA, which is essential for protein synthesis within the cell nucleus. The fragile X mental retardation mutation is characterized by an expansion of the CGG (cytosine-guanine-guanine) trinucleotide repeats within the AFF2 gene, which results in the silencing of gene expression. The analysis performed under this code can reveal different classifications of CGG repeat numbers, including normal, intermediate, pre-mutation (carrier), and full mutation. Normal CGG repeat counts range from 4 to 40, while individuals with FRAXE typically exhibit repeat counts exceeding 200. It is important to note that while CPT® Code 81171 is used for the detection of abnormal, expanded alleles, CPT® Code 81172 specifically focuses on the characterization of these alleles, including their expanded size and methylation status, providing critical information for diagnosis and management of associated conditions.