Amylo-1,6-glucosidase deficiency

= Amylo-1,6-glucosidase Deficiency = Amylo-1,6-glucosidase deficiency, also known as Glycogen Storage Disease Type III (GSD III), is a rare genetic disorder that affects the body's ability to break down glycogen, a stored form of glucose. This condition is caused by a deficiency in the enzyme amylo-1,6-glucosidase, which is crucial for glycogenolysis, the process of converting glycogen into glucose.

Pathophysiology

Glycogen is a polysaccharide that serves as a form of energy storage in humans. In individuals with amylo-1,6-glucosidase deficiency, the enzyme responsible for breaking down the alpha-1,6-glycosidic bonds in glycogen is deficient or absent. This leads to the accumulation of abnormal glycogen with short outer branches, primarily in the liver and muscles, causing hepatomegaly and muscle weakness.

Genetics

Amylo-1,6-glucosidase deficiency is inherited in an autosomal recessive pattern. The condition is caused by mutations in the AGL gene, which provides instructions for making the glycogen debranching enzyme. Both parents must carry one copy of the mutated gene to pass the condition to their offspring.

Clinical Features

The symptoms of GSD III can vary widely among affected individuals but often include:

• Hepatomegaly: Enlargement of the liver due to glycogen accumulation.
• Hypoglycemia: Low blood sugar levels, especially during fasting.
• Muscle Weakness: Due to glycogen accumulation in muscle tissues.
• Growth Retardation: Delayed growth and development in children.

Diagnosis

Diagnosis of amylo-1,6-glucosidase deficiency typically involves:

• Biochemical Tests: Measuring enzyme activity in liver or muscle tissue.
• Genetic Testing: Identifying mutations in the AGL gene.
• Liver Biopsy: Examining liver tissue for glycogen accumulation.

Treatment

There is no cure for amylo-1,6-glucosidase deficiency, but treatment focuses on managing symptoms and preventing complications:

• Dietary Management: Frequent meals high in carbohydrates to prevent hypoglycemia.
• Cornstarch Therapy: Uncooked cornstarch can provide a slow-release form of glucose.
• Liver Transplant: In severe cases, a liver transplant may be considered.

Prognosis

The prognosis for individuals with GSD III varies. With proper management, many individuals can lead relatively normal lives, although they may experience some limitations due to muscle weakness and other complications.

See Also

• Glycogen Storage Disease
• Metabolic Disorders
• Genetic Disorders

,

 Glycogen storage diseases, 
 The Metabolic and Molecular Bases of Inherited Disease, 
 2001, 
 Vol. 8 
 pp. 1521 1551,

,

 The Metabolic and Molecular Bases of Inherited Disease, 
  
 McGraw-Hill, 
 2001, 
  
  
 ISBN 978-0079130358,

NIH genetic and rare disease info

• NIH info on Amylo-1,6-glucosidase deficiency

Amylo-1,6-glucosidase deficiency is a rare disease.