Any glycogen storage disease in which the cause of the disease is a mutation in the PHKA2 gene, with no PHK activity in liver or erythrocytes. The disease is MONDO_0010598 (glycogen storage disease IXa1). Also known as: GSD type 9A, GSD type IXa, GSD9A, PHKA2 glycogen storage disease, PHKA2-related glycogen storage disease type IX, glycogen storage disease VIII, glycogen storage disease caused by mutation in PHKA2, glycogen storage disease type 9A.