Glycogen storage disease type IV

Glycogen

Glycogen storage disease type IV (GSD IV), also known as Andersen's disease, is a rare genetic disorder that affects the body's ability to properly store and break down glycogen, a form of glucose stored in the liver and muscles. This condition is part of a group of disorders known as glycogen storage diseases.

Pathophysiology

GSD IV is caused by mutations in the GBE1 gene, which encodes the enzyme glycogen branching enzyme (GBE). This enzyme is crucial for the proper formation of glycogen. In individuals with GSD IV, the deficiency or malfunction of GBE leads to the accumulation of abnormal glycogen with fewer branch points, known as amylopectin-like polysaccharide. This abnormal glycogen is less soluble and can precipitate in tissues, leading to cellular damage and organ dysfunction.

Clinical Presentation

The clinical manifestations of GSD IV can vary widely, ranging from mild to severe. The most common form is the hepatic form, which primarily affects the liver. Symptoms typically appear in early childhood and may include:

• Hepatomegaly (enlarged liver)
• Cirrhosis of the liver
• Failure to thrive
• Hypotonia (reduced muscle tone)
• Cardiomyopathy (heart muscle disease)

In severe cases, GSD IV can lead to liver failure and cardiac failure, which can be life-threatening.

Diagnosis

Diagnosis of GSD IV is based on clinical evaluation, biochemical tests, and genetic testing. Key diagnostic methods include:

• Liver biopsy to examine glycogen structure
• Enzyme assay to measure GBE activity
• Genetic testing to identify mutations in the GBE1 gene

Treatment

There is currently no cure for GSD IV. Treatment is primarily supportive and focuses on managing symptoms and preventing complications. This may include:

• Nutritional support to ensure adequate caloric intake
• Liver transplantation in cases of severe liver disease
• Regular monitoring of liver and heart function

Prognosis

The prognosis for individuals with GSD IV varies depending on the severity of the disease. Those with milder forms may have a relatively normal life expectancy with proper management, while those with severe forms may experience significant morbidity and reduced life expectancy.

Related Pages

• Glycogen storage disease
• Glycogen
• Genetic disorder
• Liver disease
• Cardiomyopathy

See Also

• Glycogen storage disease type I
• Glycogen storage disease type II
• Glycogen storage disease type III
• Glycogen storage disease type V