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Glycogen Storage Diseases and Carbohydrate Digestion Disorders

Q: Which types of glycogenoses affect muscular tissue?

Glycogenoses involving muscle tissue include: Type III glycogenosis (including subtype IIIa) — accompanied by limit dextrin accumulation in skeletal muscle due to an amylo-1,6-glucosidase defect.Glycogenosis with $\alpha$-glucosidase deficiency (acid maltase) — a lysosomal storage disease where excess glycogen is deposited in cells, most frequently affecting the heart and skeletal muscles.

For medical students2 min readUpdated 2026-10-10

Glycogen storage diseases (glycogenoses) are a broad group of inherited disorders caused by enzymatic defects responsible for glycogen synthesis, degradation, and regulation. Understanding these disorders, along with defects in disaccharide digestion, is essential for comprehending the biochemical processes of carbohydrate metabolism.

Nature of pathologyGlycogenoses are exclusively inherited disorders.

Von Gierke diseaseGlucose-6-phosphatase deficiency with accumulation of normal glycogen.

Cori diseaseAccumulation of limit dextrins (short branches) in skeletal muscle.

Andersen diseaseAbnormally long outer chains of glycogen in the liver.

Disorders of Disaccharide Digestion

Pathologies related to carbohydrate digestion and absorption occupy a significant place in clinical biochemistry. Primarily, these involve impaired breakdown of disaccharides such as lactose and sucrose, as well as disturbances in glucose handling.

These pathological states are typically classified by two main criteria:

Etiology (cause of onset) — identifying the primary factor triggering the digestive system malfunction.
Clinical presentation — evaluating the symptom complex and external manifestations experienced by the patient as a result of inadequate carbohydrate assimilation.

General Characteristics of Glycogen Storage Diseases

Glycogen storage diseases (glycogenoses) represent a specific group of inherited disorders whose pathogenesis is strictly linked to enzymatic deficiency. In a healthy body, the processes of glycogen formation and mobilization are in strict equilibrium; however, genetic defects disrupt this balance.

The defect may occur at different stages:

During glycogen synthesis, when the molecule is formed incorrectly.
During glycogen degradation, when the body cannot mobilize stored energy.
Within the regulatory system of these processes, leading to the uncontrolled accumulation of structures in organs and tissues.

Glycogen Structure Alterations in Glycogenoses

Depending on which specific enzyme is defective, the final structure of the accumulated polysaccharide and its primary site of deposition (liver or skeletal muscle) will change.

Type of Glycogenosis	Defective Enzyme	Glycogen Structure and Localization
Type I (Von Gierke disease)	Glucose-6-phosphatase	Accumulation of structurally normal glycogen in hepatocytes.
Type III (Cori disease)	Amylo-1,6-glucosidase (debranching enzyme)	Accumulation in skeletal muscle of specific molecules with short outer branches (so-called limit dextrins).
Type IV (Andersen disease)	Amylo-(1,4→1,6)-transglucosidase (branching enzyme)	Accumulation in the liver of a polysaccharide with very long outer chains and extremely sparse branching points.

As shown in the table, a defect in the debranching enzyme logically prevents the complete shortening of branches (leaving limit dextrins), while a defect in the branching enzyme deprives the molecule of a normal number of branching points, making the outer chains excessively long.

Mnemonic

To remember types: "Von Gierke — Glucose-6-phosphatase" (both start with G). "Cori — Core/Short chains" (Cori has short outer chains / limit dextrins).

Frequently asked questions

What is the biochemical cause of primary lactose intolerance?

The biochemical cause is a deficiency of the enzyme lactase (a $\beta$-glycosidase complex). The pathology arises from an inherited enzyme deficiency or age-related physiological decline in its quantity due to decreased gene expression during development. Normally, lactase is localized on the apical membrane of enterocytes, and its deficiency impairs the breakdown of the disaccharide lactose in the small intestine.

Which types of glycogenoses affect muscular tissue?

Glycogenoses involving muscle tissue include:

Type III glycogenosis (including subtype IIIa) — accompanied by limit dextrin accumulation in skeletal muscle due to an amylo-1,6-glucosidase defect.
Glycogenosis with $\alpha$-glucosidase deficiency (acid maltase) — a lysosomal storage disease where excess glycogen is deposited in cells, most frequently affecting the heart and skeletal muscles.

How does fasting blood glucose change in Type I glycogenosis?

In Type I glycogenosis (Von Gierke disease), severe fasting hypoglycemia develops in the postabsorptive period. The cause lies in an inherited defect of hepatic glucose-6-phosphatase (or glucose-6-phosphate translocase). As a result, glycogenolysis is impaired, and the release of newly formed glucose into the bloodstream is completely blocked or sharply reduced.

Which enzyme digests sucrose in the gastrointestinal tract?

Sucrose is digested in the gastrointestinal tract by the sucrase-isomaltase complex. This large enzymatic complex facilitates membrane digestion (brush border hydrolysis). It is synthesized in enterocytes, is not secreted into the lumen, and is anchored to the surface of small intestinal cells, where it finally hydrolyzes the bonds in sucrose into monomers.

What is the primary cause of glycogen storage diseases?

They are inherited disorders caused by genetic defects in enzymes that regulate glycogen synthesis and degradation.

Which enzyme is deficient in Andersen disease (Type IV)?

Andersen disease features a defect in the branching enzyme, amylo-(1,4→1,6)-transglucosidase.

What are limit dextrins, and in which condition do they form?

Limit dextrins are glycogen molecules with abnormally short outer branches. They accumulate in skeletal muscle in Type III glycogenosis (Cori disease) due to a debranching enzyme defect.

Go deeper

Classification of disaccharide digestion disorders based on etiology.
Clinical presentation features in lactose and sucrose breakdown pathologies.
The role of glucose-6-phosphatase in maintaining blood glucose levels in Von Gierke disease.
Mechanisms of glycogen branching point formation by the enzyme amylo-(1,4→1,6)-transglucosidase.