Frequently Asked Questions about GSDs
Q: Does the liver release any stored glycogen as a waste into the system?
A: Glycogen itself is not released from the liver into the body. Glycogen is a very large molecule and cannot pass through cell walls.
Q: Does glycogen store in any other organs than liver with glucose-6-phosphatase deficiency (Type I)?
A: Glucose-6-phosphatase deficiency is also known as hepatorenal glycogen storage disease. This comes from the fact that there is storage of glycogen within the kidney as well as the liver. This leads to enlargement of the kidneys, but usually does not directly affect renal (kidney) function. Some patients do develop high blood pressure but it is unclear what the cause of this is.
Q: Do many children have convulsions when their blood sugar drops?
A: Some children with glucose-6-phosphatase deficiency and debrancher deficiency who have serious manifestations do rarely have convulsions related to low blood sugar. It appears that the metabolism of most children gradually changes in order to use other energy sources and do not have convulsions even when blood sugar is low.
Q: Are there any different kinds of convulsions, seizures, or spells they can have?
A: Patients with glucose-6-phosphatase deficiency (Type I) and low blood sugar have a variety of different types of spells. These may be a direct loss of consciousness so that the patient lies motionless or drops motionless to the floor. At other times there are generalized jerking movements, chewing movements, and seizures not unlike those seen in epilepsy.
Q: Is a high protein diet important to these children?
A: There may be benefit to persons with alpha-1,4 glucosidase deficiency (Type II) and debrancher deficiency (Type III) when a high protein diet is used.
In patients with glucose-6-phosphatase deficiency protein cannot be converted to glucose, due to a deficiency of this key enzyme. Patients with GSD-I typically have 60-70% of calories as carbohydrates. It is felt at the current time that relatively low fat diets have benefit to all persons. Since lipid (fat) levels tend to be high in several of the liver forms of the glycogen storage diseases, good judgment would indicate a diet low in saturated fats and cholesterol.
Q: Does it do much harm or throw their systems off if they were to eat candy, or foods that are restricted?
A: The important thing is to eat a well-balanced nutritious diet. Occasional indiscretions are not likely to produce serious problems.
Q: When children get very sick with vomiting and nothing stays down, even glucose, what is the best solution?
A: Children with glycogen storage diseases associated with low blood sugar, and who have significant and continued vomiting usually require fluids containing glucose by vein. Your doctor can best assess this, but experienced parents are good judges. You should make plans for this in advance (have your doctor write instructions for a local 24-hour facility, either an emergency room or other emergency facility). If traveling out of your area, it is worthwhile having your physician provide written materials so this situation can be handled in a strange city.
Q: What are the chances of a person with glycogen storage disease having children of their own?
A: Many adults with glucose-6-phosphatase deficiency, debrancher deficiency, alpha-1,4 glucosidase deficiency, phosphorylase b kinase deficiency and muscle phosphorylase deficiency have children of their own. As more patients live into adulthood with better care, these numbers will likely increase.
Q: If two children at age 4 years had liver biopsies (one who has been on treatment and the other with no special treatment) could you see a difference in their livers?
A: The liver biopsy of the patient with Type I GSD who had been well controlled would contain less fat. The glycogen concentration would not be significantly changed and the enzyme defect (glu-cose-6-phosphatase deficiency) would persist.
Q: What is the life expectancy of a person with glycogen storage disease?
A: The life expectancy of persons with glucose-6-phosphatase deficiency, debrancher deficiency, and with liver phosphorylase deficiency is probably somewhat reduced although many do quite well. The big risks are kidney disease and high blood pressure. The usual patient with alpha-1,4 glucosidase deficiency and brancher deficiency dies in early childhood. Patients with muscle phosphorylase deficiency (McArdle Disease) and usual forms of phosphorylase b kinase deficiency probably have a usual life expectancy.
Q: Will the liver ever be a normal size in proportion to the body size?
A: The liver in glucose-6-phosphatase deficiency will never be normal in size. However, as the person grows taller, the liver ‘fits’ better and the abdomen is considerably less prominent. The liver in debrancher deficiency does get smaller following puberty. This is also the case of phosphorylase-b-kinase deficiency, but not well established.
Q: Will my child outgrow glycogen storage disease?
A: One never outgrows glycogen storage disease. This is a genetic defect which is permanently encoded in the genetic makeup of the person.
Q: Is research being done for a cure?
A: YES. There is a great deal of work being done in the glycogen storage diseases. Several of the key enzymes have been purified, and in some the gene has been isolated and characterized. The rapid advances in molecular genetics will impact the area of glycogen storage disease quite positively.
Q: How many patients are there?
A: Glycogen storage disease occurs in about one of 50,000 to 100,000 births. That means that there are several thousand such persons in the United States. Some patients might die before diagnosis with severe infantile forms. Some milder forms might go unrecognized.