AFF2 Repeat Expansion Testing

Description
Pathogenic CGG repeat expansions in the 5’UTR of the AFF2 gene have been associated with X-linked FRAXE intellectual disability syndrome, also known as intellectual developmental disorder, type 109. The pathogenic repeat expansions can lead to methylation of the region and subsequent silencing of AFF2 expression.
Pathogenicity is dependent upon CGG repeat length according to the following ranges 1-3:
Normal Alleles | Mutable Normal Alleles | Intermediate or Uncertain Alleles | Reduced Penetrance Alleles | Full Penetrance Alleles |
6-30 | 31-60* | 61-200* | - | 201 or more |
*Though not considered pathogenic due to limited evidence, some studies have reported intermediate and premutation range expansions in individuals with FRAXE-related conditions 4.
Alleles in the intermediate, premutation and full mutation ranges can either expand or contract during transmission to offspring.
Tests That Analyze AFF2 Repeats
- Genomic Unity® 2.0
- Genomic Unity® Whole Genome Analysis
- Genomic Unity® Lightning Genome Analysis – Neonatal
- Genomic Unity® Lightning Genome Analysis – Pediatric
- Genomic Unity® Lightning Genome Analysis – Standard
- Genomic Unity® Exome Plus Analysis
- Genomic Unity® Exome Analysis
- Genomic Unity® Epilepsy Analysis
- Genomic Unity® X-linked Intellectual Disability Plus Analysis
- IriSight® Comprehensive Analysis – Prenatal