Summary about Disease
Glycogen Storage Disease Type 0 (GSD 0) is a rare metabolic disorder affecting how the body produces and stores glycogen, the primary form of energy storage in the liver and muscles. Unlike other glycogen storage diseases that involve the breakdown of glycogen, GSD 0 involves a defect in glycogen synthase, the enzyme responsible for synthesizing glycogen. This leads to a deficiency in glycogen stores, especially in the liver. There are two types, GSD0a and GSD0b. GSD0a is liver specific, and GSD0b also involves muscle.
Symptoms
Symptoms typically appear in infancy or early childhood and are related to the body's inability to maintain normal blood glucose levels (hypoglycemia) between meals or during periods of fasting. Key symptoms include:
Hypoglycemia (low blood sugar), particularly in the morning or after fasting.
Hyperketonemia (high levels of ketones in the blood) during fasting.
Muscle fatigue or weakness
Poor growth
Seizures (due to hypoglycemia)
Increased heart rate during fasting
Nausea and vomiting
Causes
GSD 0 is caused by mutations in the GYS1 gene (for GSD0a which affects only the liver) or the *GYS2* gene (for GSD0b which affects the liver and muscles). These genes provide instructions for making glycogen synthase enzymes. Mutations in these genes result in a non-functional or poorly functioning glycogen synthase enzyme. GSD0 is inherited in an autosomal recessive pattern, meaning both parents must carry a copy of the mutated gene for their child to be affected.
Medicine Used
There is no specific medication to cure GSD 0. Treatment focuses on managing symptoms and preventing hypoglycemia through dietary management, which can include:
Frequent meals and snacks: Eating small, frequent meals throughout the day to prevent long periods of fasting.
High-protein diet: Protein is converted into glucose when glycogen is unavailable.
Uncooked cornstarch: Can be used at night to provide a slow release of glucose during sleep.
Glucose tablets or gel: For rapid treatment of hypoglycemia.
Is Communicable
GSD 0 is not communicable. It is a genetic disorder caused by a gene mutation and cannot be spread from person to person.
Precautions
The primary precautions for individuals with GSD 0 involve careful dietary management and monitoring of blood glucose levels. Specific precautions include:
Strict adherence to dietary recommendations provided by a dietitian or healthcare professional.
Regular monitoring of blood glucose levels, especially before meals, after meals, and before bedtime.
Carrying a source of fast-acting glucose (glucose tablets or gel) at all times to treat hypoglycemia.
Informing school staff, caregivers, and other relevant individuals about the condition and emergency procedures for hypoglycemia.
Avoiding prolonged periods of fasting or strenuous exercise without adequate carbohydrate intake.
How long does an outbreak last?
GSD 0 is not an "outbreak"-related disease. It's a chronic, lifelong condition. Symptoms will recur if the dietary precautions are not followed.
How is it diagnosed?
Diagnosis typically involves:
Clinical evaluation: Assessment of symptoms and medical history.
Blood tests: To measure blood glucose, ketone levels, and liver function. Elevated liver enzymes may be present.
Genetic testing: To identify mutations in the GYS1 or *GYS2* genes.
Liver biopsy: May be performed to assess glycogen content in the liver, although this is less common now with the availability of genetic testing.
Timeline of Symptoms
Infancy/Early Childhood: Symptoms often manifest in infancy or early childhood when feeding intervals become longer or when solid foods are introduced.
Throughout Life: If untreated, symptoms will continue throughout life with periods of hypoglycemia, hyperketonemia, and potential long-term complications. With proper management, the frequency and severity of symptoms can be significantly reduced.
Important Considerations
Early diagnosis and management are crucial to prevent complications such as seizures, developmental delays, and potential brain damage from repeated episodes of hypoglycemia.
Dietary management requires close monitoring and adjustments based on individual needs and activity levels.
Individuals with GSD 0 should work closely with a team of healthcare professionals, including a pediatrician, endocrinologist, geneticist, and registered dietitian.
Genetic counseling is recommended for families with a history of GSD 0 to assess the risk of recurrence in future pregnancies.