What is GSD?
The glycogen storage diseases are a group of inherited disorders of glycogen synthesis or degradation. Glycogen is the storage form of carbohydrates, and it serves as the primary fuel for the body. Glycogen is principally stored in the liver, kidneys, and muscles, and the clinical characteristics of the disease depend on the tissues which are involved. Hypoglycemia is the main manifestation of the liver forms of GSD, while muscle pain and weakness are the predominant symptoms in the muscle forms.
Will my child survive?
The prognosis for children born with most types of GSD is now excellent. Dietary treatment is the main treatment for the liver forms of GSD. Enzyme replacement is used to treat glycogen storage disease type II. Liver transplant is rarely required for any type of GSD except for GSD IV.
Will my child be able to have a normal life?
The prognosis for children and adults with GSD is excellent. Patients with the liver forms of GSD, however, will need to avoid excessive intake of sugars. Cornstarch therapy delivered frequently through the day and night helps to maintain the blood glucose concentration, and there are almost no limitations for people living with the liver forms of GSD. Patients play all sports including football, soccer, and hockey. Pregnancies in women with all types of GSD are now common. People with the muscle forms of GSD can be active, but they must work with their primary team to create a plan which does not damage the muscles.
How do you treat GSD?
The treatment depends on the type of GSD. For GSD I, cornstarch therapy or continuous feeds are used to maintain the blood glucose concentration, and the intake of fruit sugar (fructose), dairy sugar (lactose), and table sugar (sucrose) is restricted. In the other liver forms of GSD (GSD0, III, VI, IX, and XI), protein can be used as an energy source, and a high protein diet is beneficial. Restriction of sugar also is recommended. A high protein diet may also be of benefit for the muscle forms of GSD, and enzyme replacement is available for GSD II.
What affects blood sugar?
Many factors impact on the blood sugar. Frequent glucose monitoring is therefore recommended. During fasting, the carbohydrate content of the meal, illness, hot or cold weather, stress, and exercise can impact the blood sugar and cause hypoglycemia.
Can you grow out of it?
The glycogen storage diseases are genetic conditions, and they will therefore never go away. Gene therapy is presently being attempted for several of the types of GSD, and this offers hope for a new treatment for GSD in the near future.
Are carriers affected?
This is a controversial topic, but there is increasing evidence that carriers of GSD have mild manifestations of the disease. In contrast with people with the liver forms of GSD, severe hypoglycemia does not occur, but carriers may have mild shakiness and high triglycerides. People who are carriers for the muscle forms of GSD may be more prone to cramping and side effects from certain medications.
Which is optimal, cornstarch or continuous feeds at night?
This is another controversial topic. In the United States, cornstarch is the primary method for treating the liver forms of GSD, but continuous feeds are commonly in Europe and in some centers in Canada. Both treatments work, and the goal is to maintain glucose concentrations over 4.2mmol/L so that the lactic acid or ketones stay low. Cornstarch is preferred by our center because of the risk of severe hypoglycemia when a pump feed is interrupted or leaks. Cornstarch usually is not tolerated until 6-12 months of age, and cornstarch means that parents must wake up overnight to administer the feed. There is an extended release cornstarch preparation also available. It is recommended only for use overnight, and use in children under 5 years of age must be done with caution with oversite by a medical professional.
How many people across the globe have GSD? How many are treated by you and your team at the University of Connecticut?
The precise numbers of GSD patients is not known, but it is estimated that 1 in 20,000 people have either a liver or muscle form of GSD. The milder forms of GSD (GSD 0, VI, and IX) almost certainly are more common than has been appreciated. There is an unusually high rate of GSD III in the Inuit population of Canada. The team at the University of Connecticut is fortunate to treat over 500 patients with GSD who travel to Connecticut from 48 US states, 9 Canadian provinces, and 42 countries.
What are ways to help?
The Canadian Association for Glycogen Storage Disease is a critical organization. Not only does it allow families to meet each other, but the organization can help support training of more doctors in your great country. The Canadian AGSD can also help standardize the care for GSD patient across Canada since there is no consistency from province to province regarding what treatments and supplies are covered. I strongly encourage families to get active in the organization.
Bonus Questions: Have you been to Canada? Are you a hockey fan?
I have been coming to Canada very frequently over the years (usually several times per year) to work with the Canadian doctors, work on research, or to give lectures. Canada is a wonderful country, but it is a bit too cold for my Florida blood during winter.
I love all sports, but I particularly like hockey. I follow college hockey with a passion, and I (unfortunately) am a fan of the Florida Panthers. I may be one of the few Panther fans, but I have most games on the computer at night when I am working. I have stood by them for 22 years, and we will eventually start making the playoffs more than once every decade.
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