Summary about Disease
Deficiency of debranching enzyme, also known as Glycogen Storage Disease Type III (GSD III) or Cori disease/Forbes disease, is a rare genetic disorder affecting the way the body breaks down glycogen. Glycogen is a stored form of glucose (sugar) used for energy. In GSD III, the debranching enzyme, which is crucial for releasing glucose from glycogen, is deficient or non-functional, leading to an accumulation of abnormal glycogen in the liver, muscles, and sometimes the heart.
Symptoms
Symptoms can vary in severity and onset. Common symptoms include:
Hepatomegaly (enlarged liver)
Hypoglycemia (low blood sugar), especially after fasting
Muscle weakness and fatigue (myopathy)
Growth retardation in childhood
Elevated liver enzymes
Hyperlipidemia (high cholesterol and triglycerides)
Cardiomyopathy (heart muscle disease) may develop later in life.
Abdominal distention
Short stature
Delayed motor skills
Causes
GSD III is caused by mutations in the AGL gene. This gene provides instructions for making the glycogen debranching enzyme. Inheritance is autosomal recessive, meaning an individual must inherit two copies of the mutated gene (one from each parent) to develop the disease. Individuals with only one copy are carriers and typically do not show symptoms.
Medicine Used
There is no cure for GSD III, and treatment focuses on managing symptoms and preventing complications. Medications might include:
Cornstarch: Uncooked cornstarch is often used to maintain stable blood sugar levels, especially during the night. It releases glucose slowly.
Dietary management: A high-protein diet with frequent meals and snacks can help regulate blood sugar and provide alternative energy sources. Restriction of carbohydrates may be recommended.
Other medications: Depending on the complications, other medications may be used to manage liver disease, cardiomyopathy, or hyperlipidemia.
Enzyme Replacement Therapy: Currently there is no enzyme replacement therapy available.
Is Communicable
GSD III is not communicable. It is a genetic disorder and cannot be spread from person to person.
Precautions
Precautions for individuals with GSD III and their families include:
Strict adherence to the prescribed dietary regimen.
Regular monitoring of blood glucose levels.
Avoiding prolonged fasting.
Regular medical checkups to monitor liver function, muscle strength, and heart health.
Genetic counseling for families planning to have children.
Wear a medical alert bracelet.
How long does an outbreak last?
As GSD III is not an infectious disease it does not have outbreaks and therefore does not have an outbreak duration. It is a chronic, lifelong condition. Symptoms may fluctuate in severity over time, but the underlying genetic defect persists.
How is it diagnosed?
Diagnosis of GSD III typically involves:
Physical examination: Assessing symptoms like hepatomegaly and muscle weakness.
Blood tests: Measuring blood glucose, liver enzymes, cholesterol, and triglycerides.
Muscle biopsy: Examining muscle tissue for abnormal glycogen accumulation.
Liver biopsy: Examining liver tissue for abnormal glycogen accumulation.
Enzyme assay: Measuring the activity of the debranching enzyme in blood cells or tissue samples.
Genetic testing: Analyzing the AGL gene for mutations.
Timeline of Symptoms
The timeline of symptoms can vary, but generally:
Infancy/Early Childhood: Hepatomegaly, hypoglycemia, and growth retardation may be apparent.
Childhood/Adolescence: Muscle weakness and fatigue may become more noticeable. Liver enzyme elevations persist.
Adulthood: Cardiomyopathy, liver cirrhosis, and other complications may develop.
Symptoms do not always progress linearly, and some individuals may experience milder symptoms throughout their lives.
Important Considerations
Early diagnosis and management are crucial to minimize long-term complications.
Dietary management is the cornerstone of treatment.
Regular monitoring of liver function, muscle strength, and heart health is essential.
Genetic counseling is important for families with a history of GSD III.
Research is ongoing to develop new therapies for GSD III, including gene therapy.
Patient support groups can provide valuable information and emotional support.