Glycogen Storage Diseases

Glycogenoses

Epidemiology and Etiology:

· metabolic defect in the synthesis or catabolism of glycogen

· glucose-6-phosphatase deficiency – type Ia – von Gierke

· muscle phosphorylase deficiency – type V – McArdle

· muscle phosphofructokinase deficiency – type VII

· α-glucosidase (acid maltase) deficiency – type II – Pompe

· debrancher deficiency – type III - Forbes

· degradation of glycogen is performed by distinct phosphorylases in the liver and muscle

· glycogen is also degraded in the lysosomes by acid maltase

Common sites:

· may be limited to a few tissues, may be more wide-spread while not affecting all tissues, or may be systemic in distribution

· liver

· type I – von Gierke

· striated muscle

· type V – McArdle

· type VII

· systemic

· type II – Pompe

· type III – Forbes

Gross features:

· hepatomegaly

· systemic forms:

· organomegaly

· cardiomegaly is most prominent in Pompe

Histologic features:

·

Immunophenotype:

Marker:

Sensitivity:

Specificity:

Molecular features:

·

Other features:

· Hepatic forms:

· Hypoglycemia

· Myopathic forms:

· muscular weakness owing to impaired energy production

· muscle cramps after exercise

· systemic forms:

· death in early life

References:

· Kumar V, Fausto N, Abbas A. Robbins & Cotran Pathologic Basis of Disease, Seventh Edition. 7th ed. Saunders; 2004:1552.