Increased K+ release during exercise in myotonic dystrophy type 1 (DM1) but not type 2 (DM2, PROMM)

Aims: Excessive K+ increase upon exercise was previously described in myotonic dystrophy, but not in non-dystrophic myotonias or other muscular dystrophies. However, at that time the differentiation into myotonic dystrophy type 1 (DM1) or type 2 (DM2) was not yet possible. Objective: Resting venous and interstitial (intramuscular) lactate and K+ levels were measured in patients with genetically defined DM1 (n=6) and DM2 (n=6). Control groups included mitochondrial disorders (n=9) and healthy volunteers (n=9). In all individuals venous and interstitial lactate and K+ were analysed upon standardized forearm exerci…