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Glycogen-Storage Disease Type VI
Sunday, 06 February 2005
Sunday, 06 February 2005
Hers disease

What

Glycogen-storage disease type VI (GSD VI) is a rare, inherited condition characterized by low blood sugar (hypoglycemia) during periods of brief fasting. The human body uses sugar (glucose) as its main source of energy. During fasting, blood sugar levels must be maintained at adequate levels in order for the body to function properly. After eating, sugar from the digestion of food is stored in the muscles and liver in a form called glycogen. During fasting, glycogen is broken down by an enzyme named liver phosphorylase. In GSD VI, this enzyme is absent or not fully functioning and low blood sugar levels result. The liver also increases in size because the glycogen, which cannot be broken down, builds up in the liver.

Who

One in 83,000 newborns has GSD VI. Girls and boys of all races and ethnicities are affected equally.

Signs and Symptoms

The severity of symptoms varies from child to child. Low blood sugar levels usually start after the age of 3-4 months when feedings are more spaced out. Low blood sugar levels can cause poor feeding, difficulty breathing, irritability, jitteriness, trembling, decreased temperature, sweating, lethargy, dizziness, headache, confusion, fainting and seizing. Episodes of low blood sugar later in childhood are often triggered by illness, vomiting, or fever, as children are often unable to eat in these situations. Development is usually normal; however, repeated and long periods of low blood sugar can cause damage to the brain. Also, poor growth and short stature may result. The liver will also increase in size as the glycogen, which cannot be broken-down, builds up.

Possible Causes

GSD VI is inherited in an autosomal recessive manner. This means that two genes with a change (mutation) are necessary to cause this disorder. The parents of an affected child are usually healthy, but each parent carries a copy of the changed gene. If both parents are carriers, there is a 25% chance that each of their children will develop this disease. GDS VI is not contagious or preventable. GSD VI is caused by a mutation in the gene for the liver phosphorylase enzyme, which is located on chromosome 14.

Diagnosis

Blood testing during periods of brief fasting will show low blood sugar levels. Liver enzyme levels are often elevated due to ongoing liver injury. To diagnose GSD VI, the presence of liver phosphorylase in the blood must be measured. An abdominal ultrasound or CT scan may reveal an enlarged liver.

Treatment

No specific treatment or cure is available for GSD VI. Frequent meals, plentiful in carbohydrates which contain a lot of sugar, will reduce liver size, prevent low blood sugar (hypoglycemia) and allow for normal growth and development. If hypoglycemia occurs, drinking fruit juice can be used to raise blood glucose levels. If the child is unable to drink during illness, getting sugar and fluids through the vein is an important alternative. Research is being done to find a treatment by enzyme or gene replacement. For children with severe cases of GSD VI, liver transplantation can be performed to eliminate the enzyme defect.

Prognosis

With early diagnosis and appropriate treatment, the prognosis is very good. Keeping blood sugar levels stable decreases the chance of liver disease later in life.

Connect with other parents

In the spirit of community and support, Madisons Foundation offers the unique service of connecting parents of children with rare diseases. If you would like to be connected to other parents of children with this disease, please fill out this brief form.

Weblinks

Association for Glycogen Storage Disease http://www.agsdus.org Provides information, education and email networking. Organic Acidemia Association http://www.oaanews.org Voluntary support group which represents children and adults with these disorders, their families and caregivers. CLIMB (Children Living with Inherited Metabolic Diseases) http://www.CLIMB.org.uk National organization providing information, news, financial support, and networking. March of Dimes Birth Defects Foundation http://www.marchofdimes.com Non-profit organization providing support groups, education, information about research studies, counseling, and family networking. NIH/National Institute of Diabetes, Digestive and Kidney Diseases Endocrine Diseases Metabolic Diseases Branch http://www.niddk.nih.gov National organization providing information, support, and newsletters.

Google Search for Glycogen-Storage Disease Type VI

References and Sources

www.emedicine.com/med/topic912.htm www.whonamedit.com/synd.cfm/2506.html www.agsdus.org/html/typevihers.htm www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=232700