In a prospective series of 112 unrelated patients, we found that approximately 20% of people with Friedreich ataxia have at least one such expanded composite allele. Other minor sequence interruptions in the expanded GAA repeat were detected in a further 10% of patients. Most expanded composite alleles revealed by longread genome sequencing are not detectable by standard PCR-based testing, and have therefore remained hidden despite their relatively high prevalence. This results in erroneous genotyping of patients and heterozygous carriers.
Sunday, December 28, 2025
Unrecognized high prevalence of expanded composite repeats in Friedreich ataxia
Devore MC, Lam C, Wiley G, Park CC, Lynch DR, Bidichandani SI. Unrecognized high prevalence of expanded composite repeats in Friedreich ataxia. Hum Mol Genet. 2025 Dec 23:ddaf190. doi: 10.1093/hmg/ddaf190. Epub ahead of print. PMID: 41432640.
