Glycogen storage disease type IIIa presenting as non-ketotic hypoglycemia: use of a newly approved commercially available mutation analysis to non-invasively confirm the diagnosis.

Glycogen storage disease type III (GSD-III) is an autosomal recessive disorder caused by the lack of amylo-1,6-glucosidase (AGL), one of the catalytic domains of the glycogen debranching enzyme. Deficiency of this enzyme classically results in hepatomegaly and ketotic hypoglycemia. The diagnosis of the disorder was previously confirmed with a liver biopsy demonstrating abnormal liver glycogen content and absent enzyme activity.