Glycogen storage disease type 0, liver

Alternate names

Liver GSD 0; Liver glycogen storage disease 0; Hepatic glycogen synthase deficiency; Liver glycogen synthase deficiency

Definition

Glycogen storage disease type 0, liver (liver GSD 0), a form of glycogen storage disease (GSD), is a rare abnormality of glycogen metabolism (how the body uses and stores glycogen, the storage form of glucose). It is a condition caused by the body's inability to form a complex sugar called glycogen, which is a major source of stored energy in the body.

Epidemiology

The prevalence of GSD 0 is unknown; fewer than 10 people with the muscle type and fewer than 30 people with the liver type have been described in the scientific literature. Because some people with muscle GSD 0 die from sudden cardiac arrest early in life before a diagnosis is made and many with liver GSD 0 have mild signs and symptoms, it is thought that GSD 0 may be underdiagnosed.

Cause

It is caused by a deficiency of the enzyme glycogen synthetase in the liver, due to mutations in the GYS2 gene. The GYS2 gene provides instructions for making liver glycogen synthase, which is produced solely in liver cells. Glycogen that is stored in the liver can be broken down rapidly when glucose is needed to maintain normal blood sugar levels between meals.

Gene mutations

• Mutations in the GYS2 gene lead to a lack of functional glycogen synthase, which prevents the production of glycogen from glucose.
• Mutations that cause GSD 0 result in a complete absence of glycogen in either liver or muscle cells.
• As a result, these cells do not have glycogen as a source of stored energy to draw upon following physical activity or fasting.
• This shortage of glycogen leads to the signs and symptoms of GSD 0.

Inheritance

Autosomal recessive inheritance, a 25% chance

This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.

Onset

Symptoms typically begin in infancy or in early childhood.

Signs and symptoms

Symptoms may include drowsiness, sweating, lack of attention, fasting hypoglycemia associated with hyperketonemia, seizures, and other findings.

For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. 30%-79% of people have these symptoms

• Glycosuria(Glucose in urine)
• Irritability(Irritable)
• Ketonuria
• Ketosis(High levels of ketone bodies)
• Ketotic hypoglycemia
• Postprandial hyperglycemia

5%-29% of people have these symptoms

• Abnormality of the gastrointestinal tract
• Elevated hepatic transaminase(High liver enzymes)
• Failure to thrive(Faltering weight)
• Global developmental delay
• Hyperlipidemia(Elevated lipids in blood)
• Lethargy
• Seizure
• Short stature(Decreased body height)

Diagnosis

Molecular Genetics Tests

• Sequence analysis of select exons
• Deletion/duplication analysis
• Sequence analysis of the entire coding region
• Targeted variant analysis

Treatment

Treatment involves a specific diet that includes frequent meals with high protein intake during the day, and uncooked starch in the evening.

Prognosis

The prognosis is usually favorable when the disease is correctly managed.

NIH genetic and rare disease info

• NIH info on Glycogen storage disease type 0, liver

Glycogen storage disease type 0, liver is a rare disease.

Glycogen storage disease type 0, liver Resources
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