Mutations in G6PC, one of the three genes encoding the G6Pase catalytic subunits in humans (G6PC1, G6PC2, and G6PC3), cause glycogen storage disease type Ia (GSD-Ia), which is characterized by neuropathy, hepatic adenocarcinoma, and osteopenia [118,119,120]. The gene discussed is G6PC1; the disease is neuropathy.