Glycogen Storage Disease Type I
What is Glycogen Storage disease?
Glycogen storage diseases (GSDs) are a group of inherited genetic disorders that cause glycogen to be improperly formed or released in the body. They are characterized by the accumulation of abnormal amounts or types of glycogen in tissues.
Glucose is a simple sugar, which is a form of carbohydrate. It is found in many foods and is the main source of energy for our bodies. Glycogen is the storage form of glucose in our bodies. Glycogen storage diseases are due to either a deficiency or blockage of an enzyme that is important in converting glucose to glycogen so it can be stored in the body for later use. The main places glycogen is stored in the body includes the liver and muscle cells.
The main types of GSDs are categorized by number and name. They include:
- Type I (Von Gierke disease, defect in glucose-6-phosphatase) – this is the most common type of GSD, and accounts for 90% of all GSD cases
- Type II (Pompe’s disease, acid maltase deficiency)
- Type III(Cori’s disease, debrancher enzyme deficiency)
- Type IV (Andersen’s disease, brancher enzyme deficiency)
- Type V (McArdle’s disease, muscle glycogen phosphorylase deficiency)
- Type VI (Hers’ disease, liver phosphorylase deficiency)
- Type VII (Tarui’s disease, muscle phosphofructokinase deficiency)
- Type IX (liver glycogen phosphorylase kinase deficiency)
Since glycogen is primarily stored in the liver or muscle tissue, GSDs usually affect functioning of the liver, the muscles, or both.
What is Von Gierke disease?
Von Gierke disease is a form of glycogen storage disease and may be called many other names. This includes:
- Gierke’s disease
- van Creveld-von Gierke disease
- von Gierke’s disease
- Glucose-6-phosphatase deficiency
- Glycogen storage disease I
- glycogen storage syndrome
- glycogenosis type I
- hepatonephromegalia glycogenic
- hepatorenal glycogenosis
- liver glycogen disease.
Von Gierke’s is relatively common in a group of hereditary glycogen-storage diseases. This progressive disease is an inborn error of glycogen metabolism due to glucose-6-phosphatase (G6P) deficiency, involving chiefly the liver and kidneys. The liver may become huge and contain as much as 15 percent of glycogen.
What are the symptoms?
The symptoms are usually present at birth or appear shortly thereafter. A very long list of symptoms and clinical signs includes failure to thrive, convulsions (hypoglycaemic), retarded growth without disproportion; prominent abdomen due to massive hepatomegaly; adiposity with accumulation of fat in the cheeks, buttocks, and subcutaneous tissues; bleeding tendency; epistaxis; occasionally, steatorrhea; lumbar lordosis; adiposity; skin yellowish xanthomas over joints and buttocks. The muscles are flabby and poorly developed. Gout-related signs.
How many people does it affect?
The disorder occurs in only about 1 in 200,000 persons, affecting both sexes. Afflicted individuals who survive into adulthood suffer primarily from hyperuricaemia and hepatoma. The syndrome is transmitted as an autosomal recessive trait. This was the first recessively inherited disorder shown to be due to deficient activity of a specific intracellular enzyme.
How is it diagnosed?
Several specialized tests are used to confirm a suspected diagnosis of metabolic disease:
- Blood tests can be used to detect the presence of certain chemicals in the blood that may indicate some metabolic diseases.
- An exercise test is used to monitor a person’s response to intense or moderate exercise. Blood samples are taken during exercise for testing.
- Electromyography (EMG) uses small needle electrodes to measure the electrical currents in a muscle as it contracts. While an EMG can’t definitively diagnose metabolic disease, it can be used to rule out a number of other types of neuromuscular disease that cause similar patterns of weakness.
- A muscle biopsy requires the removal of a small piece of muscle tissue for microscopic analysis. The procedure is done either surgically, with an incision to expose the target muscle, or with a needle. A skin biopsy is also sometimes performed. A muscle biopsy will show a deficiency of the muscle phosphofructokinase enzyme and a modest accumulation of glycogen found
- Other tests that may be needed include an electrocardiogram to test heart function, and brain imaging studies such as CT or MRI scans.
- Genetic tests, using a blood sample, can analyze the person’s genes for particular defects that cause metabolic disease, but these tests often aren’t necessary for diagnosis or for determining treatment.
Is there any treatment?
This is just a guide. Your doctor will develop a treatment regimen based on your specific symptoms.
The goal of treatment is to maintain normal blood glucose levels. This may be done with:
- A nasogastric infusion of glucose in infants and children under age two
- Dietary changes, including:
- In children over age two, frequent small carbohydrate feedings are given throughout the day. This may include uncooked cornstarch. (Uncooked cornstarch provides a steady slow-release form of glucose.)
- Elimination of foods that are high in fructose or lactose (type I only)
- Allopurinol (Aloprim, Zyloprim) may be prescribed to reduce uric acid levels in the blood. This is done to prevent gout and kidney stones.
- Type IV is sometimes treated with liver transplantation.
Is there any way to prevent Von Gierke disease?
There is no way to prevent GSDs. However, early treatment can help control the disease once a person has it. If you have a GSD or a family history of the disorder, you may want to consult a genetic counselor when deciding to have children.