We read with great interest the article by Nokelainen and colleagues1 on a unique case of a patient with phenotypes of both myotonic dystrophy (DM) and progressive myoclonus epilepsy of the Unverricht-Lundborg type (EPM1). Each of these 2 disorders was caused by a mutation with an expanded repeat sequence. Coexistence of 2 expanded repeat sequences in different loci is quite rare and informative in considering the pathogenesis of genetic diseases caused by repeat expansion, as the editorial by Johnson2 indicated. In this case, expanded CTG and CCCCGCCCCGCG fall into the type II group of repeat sequences3 and might produce a phenotype as the sum of DM and EPM1.
Kageyama T, Shimohama S, Kawamata J. Coexistence of 2 Different Type I Repeats. Arch Neurol. 2001;58(6):1022. doi: