MONDO_0700291 (glycogen storage disease IX) can be described as follows. A group of inborn errors of glycogen metabolism that is clinically and genetically heterogeneous. This group comprises GSD due to liver phosphorylase kinase (PhK) deficiency, GSD due to muscle PhK deficiency and GSD due to liver and muscle PhK deficiency. Also known as: GSD IX, GSD type 9, GSD type IX, GSD9, GSDIX, glycogen storage disease 9, glycogen storage disease type 9, glycogen storage disease type IX.