Overview of repeats
In one study (Lafreniére et al., 1997), it was reported that Unverricht-Lundborg disease (ULD), also known as progressive myoclonic epilepsy type 1 (EPM1), is caused by an bi-allelic expansion of a dodecamer repeat (CCCCGCCCCGCG) in the 5' flanking region of the cystatin B gene (CSTB). The insertions were approximately 600-900 bp, corresponding to about ~50-75 dodecamer repeats, while the normal gene has three repeats.
In another study (Lalioti et al., 1998) repeats ranging from approximately 30 to 75 were detected in affected individuals. However, in the case of an individual who had 30 repeats in the smaller allele, there were 52 repeats in the other allele (mean 41). The mean expansion size ranged from 46 to 75 across all patients. The age of onset ranged from 8 to 15 years, and no correlation between the size of the expansion and the age of onset was detected.