Limit dextrinosis

Limit Dextrinosis

Limit dextrinosis, 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 glycogen debranching enzyme, which is necessary for the complete degradation of glycogen into glucose.

Pathophysiology

Glycogen is a polysaccharide that serves as a form of energy storage in humans. In individuals with limit dextrinosis, the deficiency of the glycogen debranching enzyme leads to the accumulation of abnormal glycogen with short outer branches, known as limit dextrins, in the liver and muscles. This accumulation can cause hepatomegaly (enlarged liver), hypoglycemia (low blood sugar), and muscle weakness.

Genetics

Limit dextrinosis is inherited in an autosomal recessive pattern, meaning that an individual must inherit two copies of the defective gene, one from each parent, to be affected by the disease. The gene responsible for this condition is the AGL gene, which provides instructions for making the glycogen debranching enzyme.

Clinical Features

The symptoms of limit dextrinosis can vary widely among affected individuals but often include:

• Hepatomegaly: Enlargement of the liver due to glycogen accumulation.
• Hypoglycemia: Episodes of low blood sugar, especially during fasting.
• Muscle Weakness: Due to glycogen accumulation in muscle tissue.
• Growth Delay: Some children may experience delayed growth and development.

Diagnosis

Diagnosis of limit dextrinosis typically involves a combination of clinical evaluation, biochemical tests, and genetic testing. Liver biopsy may show the characteristic accumulation of limit dextrins. Genetic testing can confirm mutations in the AGL gene.

Treatment

There is currently no cure for limit dextrinosis, but treatment focuses on managing symptoms and preventing complications. Dietary management is crucial and may include:

• Frequent Meals: To prevent hypoglycemia, individuals may need to eat frequent meals high in carbohydrates.
• Cornstarch Therapy: Uncooked cornstarch can provide a slow-release form of glucose.
• High-Protein Diet: To support muscle health and growth.

Prognosis

The prognosis for individuals with limit dextrinosis varies. With proper management, many individuals can lead relatively normal lives, although they may need to adhere to dietary restrictions and monitor their blood sugar levels closely.

Research

Ongoing research is focused on better understanding the genetic and biochemical basis of limit dextrinosis, as well as developing potential therapies, including enzyme replacement therapy and gene therapy.

See Also

• Glycogen storage disease
• Autosomal recessive disorder
• Hypoglycemia

External Links

• National Organization for Rare Disorders
• Genetic and Rare Diseases Information Center

NIH genetic and rare disease info

• NIH info on Limit dextrinosis

Limit dextrinosis is a rare disease.