Disorders of Carbohydrate Metabolism

Glycogen Storage Diseases

Abnormal metabolism of glycogen, glucose. Due to specific enzyme deficiency (Table 85.1). May present with: fasting hypoglycemia, pathologic glycogen storage (e.g., hepatomegaly), or organ dysfunction (e.g., liver disease, myopathy).

Table 85.1 Selected Glycogen Storage Diseases

Disease	Affected tissues	Mode of transmission	Clinical presentation
Glucose-6-phosphatase deficiency (Type I, von Gierke)	Liver, kidney	AR	Severe hypoglycemia; hepatomegaly
Infantile acid maltase deficiency (Type II, Pompe)	Generalized	AR	Lethal infantile neuromyopathy: severe cardiomyopathy, hypotonia, respiratory failure, death <1 year.
Acid maltase deficiency, juvenile/adult	Generalized	AR	Slowly progressive myopathy; often with respiratory insufficiency
Debrancher enzyme deficiency (Type III, Cori/Forbes)	Generalized	AR	Hepatomegaly; fasting hypoglycemia; limb weakness
Branching enzyme deficiency (Type IV, Andersen)	Generalized	AR	Hepatosplenomegaly; liver cirrhosis; liver failure
Muscle phosphorylase deficiency (Type V, McArdle)	Skeletal muscle	AR	Exercise-induced myalgia, cramps; myoglobinuria
Phosphoglycerate kinase (PGK) deficiency	Generalized	XR	Variable: hemolytic anemia; seizures; mental retardation; exercise intolerance; myoglobinuria
Glycogen synthetase deficiency	Liver	AR	Severe fasting hypoglycemia with ketosis
AR, autosomal recessive; XR, X-linked recessive.