Impaired glycogen breakdown and synthesis in phosphoglucomutase 1 deficiency

The second wind phenomenon has been considered to be pathognomonic for McArdle disease, but we demonstrate that it can also be present in PGM1 deficiency. We show that severe loss of PGM1 activity causes blocked muscle glycogenolysis that mimics McArdle disease, but may also limit glycogen synthesis, which broadens the phenotypic spectrum of this disorder.