Glycogen storage disease type 1a (GSD1a, OMIM: 232200) is an autosomal recessively inherited inborn error of metabolism defined by impairment of glucose-6-phosphatase-α (G6Pase-α, encoded by the G6PC gene) with a prevalence of approximately 1 in 100,000 individuals (2–4). Here, G6PC1 is linked to Glycogen storage disease due to glycogenin deficiency.