GSK3B and myotonic dystrophy type 1: To determine if the increase in active GSK3β in the PBMCs in patients with adult-onset DM1 correlates with the muscle weakness determined at the time of blood collection, we compared the average active GSK3β levels in adult-onset DM1 patients with no previously reported myotonia and mild muscle phenotype, based on the grip and ankle strength tests (Figure 2A,B), which carry 68–100 CTG repeats, with those in a group of DM1 patients showing moderate muscle symptoms including myotonia and weakness (patients with 131, 163, >200 and ~500 CTG repeats).