In myotonic dystrophy type 2 (DM2), an association has been reported between early and severe myotonia and recessive chloride channel (CLCN1) mutations.
Because the two genes segregate independently, the prevalence of CLCN1 mutations in the total DM2 patient population is, by definition, the same as in the control population.
The mutant RNA transcripts of DM1 and DM2 aberrantly affect the splicing of the same target RNAs, such as chloride channel 1 (ClC-1) and insulin receptor (INSR), resulting in their shared myotonia and insulin resistance.