|Number of repeats||Counts (alleles)||Percentage|
Overview of repeats
Oculopharyngodistal myopathy 4 (OPMD4) is an adult-onset muscle disease. In 2022, two papers were published (Yu et al., 2022 and Zeng et al., 2022), both which reported an expanded GGC allele in OPMD4 patients. The expansion was found in the 5' UTR of RILPL1 gene.
Yu and colleagues found a CGG expansion in RILPL1 gene in two unrelated OPDM-affected individuals and determined this as a causative mutation of OPDM4. Next, they analysed 20 other OPDM-affected individuals with unknown genetic cause and found another nine individuals with a similar expansion. The expansion all eleven OPDM-affected individuals ranged from 139 to 197 repeats. Finally, by analysing 200 normal controls (Chinese) they determined the normal length of CGG repeats in this cohort to be between 9 to 16 repeats (Yu et al., 2022).
Similarly, Zeng and colleagues found CGG repeat expansion in six patients from two unrelated Chinese Han families who had typical OPMD phenotype. Repeats in those patients ranged from 135 to 190 repeats, being in line with the paper pubilshed by Yu et al. The normal distribution of CGG repeats was between 10 and 17 in 465 controls (Chinese) and 4-20 in individuals from the 1000 Genomes Project (Zeng et al., 2022).