SPEG and myopathy: It was discovered in a mouse that SPEG dysfunction produces a myopathy by affecting Ca2+ current function of the voltage sensor, calcium release from the SR and consequently reducing muscle contractility.24, 25 Recent studies confirmed that the protein kinase domain II is actually the key domain that controls the Ca2+ re‐uptake through regulating SERCA2a.26 These indicate that dysfunction of protein kinase domain II of SPEG may cause CNM because of unbalanced calcium homeostasis through the SERCA2a pathway.