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Glycogen type 1A or Von Gierke disease

Glucose is a simple sugar and the primary source of energy in our organism and glycogen is the storage form of glucose.

Glycogen storage diseases are a group of hereditary genetic disorders. Because of them, glycogen breaks away from the body incorrectly and consequently, increases abnormal amounts or types of glycogen in the body. Glycogen is stored principally in the liver or in the muscular tissue and for this reason, GSD generally affects the workings of the muscles or liver.

The principal types of GSD are classified by number and name, among which is Type I (GSD I) or Von Gierke disease. Itis the most common of the glycogen storage diseases. This genetic disease results from deficiency of the enzyme glucose-6-phosphate, and has an incidence in of approximately 90% of all GSD cases.

Type I glycogen storage disease (GSD I) occurs when the body lacks the protein enzyme glucose-6-phosphate that releases glucose from glycogen. Normally the enzymes help convert glucose into glycogen for storage (glycogen genesis); other enzymes convert the glycogen back to glucose when the body needs energy (glycogenolysis). In GSD, some of these enzymes are defective, insufficient, or non-existent and abnormal glycogen is accumulated in the liver or muscular tissues.

GSD-1A can be found in both males and females and it is inherited, which means it is passed down through families. If both parents carry the defective gene associated with this condition, each of their children has a 25% chance of developing the disease.

The principal causes of death from this disorder are hyperglycemic seizures and/or severe acidosis.

SIGNS AND SYMPTOMS

Children with this condition are usually diagnosed before age 1 and have multiple problems such as symptomatic hypoglycemia, hepatomegaly, nephromegaly, puffy cheeks, and muscle weakness and delayed growth.

Hypoglycemia, more or less severe, can be accompanied by lactic acidosis and hyperlipidemia, which includes a raise in triglycerides like those of cholesterol.

Hyperlipidemia can produce eruptive xanthomas and typical retinal changes. Hepatomegaly and nephromegaly are important while splenomegaly is discrete.

Hyperuricemia, as a result of the increase of the metabolism of the purines and renal insufficiency, is most important in those individuals who are affected after adolescence. Liver adenomas usually develop, which in some cases, can be malignant. There is also a moderate anemia due to frequent hemorrhaging and diathesis caused by disorders of the platelet function.

Diarrheas are frequent due to the intestinal malabsorption of the glucose and osteoporosis because of chronic acidemias and renal insufficiency of these patients.

Diagnosis is made by an evaluation of the glucose-6-phosphate enzyme in the liver and the demonstration of the glycogen aggregates in the cytoplasm of the hepatocytes. Currently, a prenatal diagnosis is not possible.

RISK FACTORS

The principal risk factor for developing GSD is to have a family member with this disorder. Statistically, if both parents are carriers of the mutated gene, each one of the children has a 25% chance of inheriting the disorder; 50% will be carriers without developing the disorder and 25% will neither develop the disorder nor be carriers.

PREVENTION

Strategies for preventing the GSD disorder are not known; however, an adequate treatment can help to control the illness once a person has developed it. If a person has GSD, or has family members with GSD, and wishes to have children, a genetic test and consultation will help to determine the risk the children have of developing the disease.

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