Patients 1 and 3 shared the same pathogenic variant PHKA1 (c.2806C>T, p.Arg936Ter) in exon 25; patient 3 suffered from exercise intolerance and myalgia in childhood in the setting of a normal CK level while patient 1 presented with delayed developmental milestones, myalgia, and dysphagia in childhood with CK levels 1.2× the upper limit of normal. This evidence concerns the gene PHKA1 and Myalgia.