FXN and Friedreich ataxia: For example, approximately 1%–4% of individuals with Friedreich ataxia have an abnormally expanded GAA repeat in the disease-causing range on 1 frataxin allele and another intragenic pathogenic variant on the other allele.34,35 More recently, noncoding GCA and GCC repeat expansion in compound heterozygous state with a second missense or truncating variant were identified as causative of 2 other rare inherited conditions, glutaminase deficiency36 and Baratela-Scott syndrome,37 respectively, leading to a clinical phenotype indistinguishable from patients with biallelic pathogenic variants.