G6PC1 and glycogen storage disease I: Moreover, GYS2 with its missense SNP rs121918420 (Orho et al., 1998), and G6PC with another missense SNP rs1801175 (Froissart et al., 2011) are associated with Glycogen storage disease type 1 (GSD1) that is a disorder characterized by severe fasting hypoglycaemia.