The most commonly identified predisposing conditions of ER are deficiencies of carnitine palmitoyltransferase II (CPT2 gene, OMIM *600650), myophosphorylase (McArdle disease, PYGM gene, OMIM *608455), and myoadenylate deaminase (AMPD1 gene, OMIM +102770). This evidence concerns the gene PYGM and glycogen storage disease V.