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Abstract

Glycogen storage disease type IXa (GSD IXa) is a congenital disorder of glycogen metabolism caused by pathogenic variants of the PHKA2 gene, which encodes the ?-subunit of liver phosphorylase kinase. This study presents six cases of boys with hemizygous variants in the PHKA2 gene. At presentation, manifestations included recurrent ketotic hypoglycemia (n= 4), hepatomegaly (n= 3), hypertriglyceridemia (n= 3) and elevated aminotransferases (n= 2), with evidence of mild liver fibrosis in two cases. Supplementation with glucose polymers and proteins, alongside the avoidance of prolonged fasting, led to clinical improvement and normalization of laboratory results. These cases demonstrate the phenotypic variability of GSD IXa, which makes differential diagnosis with other causes of recurrent ketotic hypoglycemia. The data reinforce the value of detecting hypoglycemia with simultaneous determination of ketonemia. Corroboration of the diagnosis through genetic testing is useful for guiding treatment and enabling family counselling.