MYH14 and myasthenia gravis: A decline of the R1500P EDL peak force to approximately 90% and approximately 85% by the 10th and 29th tetanus stimuli compared with the more stable percentage measured for the βWT muscle (Figure 2B) confirmed that the myosin mutant provoked fatigue and suggested that in patients with MPD1, muscle fatigue and weakness can occur concurrently, as reported, for example, in patients with myasthenia gravis (32).