Download Glycogen Storage Disease – Type I

Glycogen Storage Disease – Type I
What is glycogen storage disease type I?
Glycogen storage disease type I (GSDI) is a disorder caused by a deficiency of an enzyme which helps in
maintaining a normal blood glucose level (sugar concentration) during fasting. The body stores extra glucose in a
form called glycogen. When the body needs more sugar to maintain blood sugar levels and energy it converts
glycogen back into glucose. In GSDI enzymes which help convert glycogen to glucose do not work properly and
this leads to the accumulation of glycogen and fat in the liver and kidneys, resulting in enlargement of these
organs. There are two subtypes of this disease: GSDIa and GSDIb. The subtype is decided based on which enzyme
in the process of glycogen conversion process if malfunctioning. GSDI is referred to as an inborn error of
metabolism, meaning that people are born with the condition. It can be inherited in families in an autosomal
recessive fashion.
What the symptoms and complications are of glycogen storage disease type I?
Most people with GSDI become unwell as infants and can have an abnormally large liver, vomiting, seizures and
difficulties growing. Children with this disorder typically have delayed growth and puberty, a greatly enlarged liver,
and a swollen abdomen. Children with the condition also typically have what is called a “doll-like face” with fat
cheeks, relatively thin arms and legs, short stature, and bulging abdomen. Many gave gut problems such as
diarrhea or irritable bowel disease. Some individuals have dysfunction of their blood cells which causes the blood
not to clot properly and leads to easy bleeding. Other blood cells may not work properly and cause anemia, or
decreased ability to fight infection.
Long-term complications of untreated GSDI include short stature, weak bones, delayed puberty, joint problems
caused by uric acid crystals collecting in joints (known as gout) , kidney disease, high blood pressure in the vessels
connecting the heart and lung, and liver tumours with an increased risk for them to become cancerous. Normal
growth and puberty may be expected in treated children. Most individuals with GSDI live into adulthood.
How is glycogen storage disease type I diagnosed?
Routine blood work will reveal the characteristic abnormalities of low blood sugar concentration accompanied by
high lactate levels in the blood and higher than normal levels of lipids and uric acid. Genetic testing on a sample
of DNA can determine which specific gene is involved and the type of GSD that a person has.
How is glycogen storage disease type I treated?
Individuals with GSDI should be followed regularly by a specialty clinic that deals with metabolic disorders and
should meet frequently with metabolic dietitians. Diet should be low in simple sugars such as fructose and
sucrose, with galactose and lactose intake limited to about a serving a day. Medical nutritional therapy is used to
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maintain normal blood glucose concentrations to prevent low blood sugars, and provide optimal nutrition for
growth and development. One of the most important approaches to nutritional therapy includes the need to
prevent low blood sugars by increasing the frequency of meals and snacks and by eating foods that contain slowly
metabolized starches such as cornstarch. Overnight continuous feeding of nutrition products containing complex
carbohydrates is also typically needed to prevent low blood sugars while a client is also sleeping. This is important
as low blood sugars can cause seizures, coma and possibly death. Consultation with a metabolic dietitian is
important to prevent this.
A medication called allopurinol is used to prevent gout if dietary therapy is not able to control uric acid levels and
crystal formation. As well, cholesterol lowering medications are given when cholesterol levels are elevated despite
maintaining a good diet and exercise. Supplementation can be given to help prevent development of kidney stones
and blood pressure medications may be used to help protect the kidneys from becoming damaged. In the event
that the liver and kidneys begin to fail, liver and kidney transplantation is considered an effective therapy for some
individuals with glycogen storage disease.
Reviewed in 2015.
3100 Steeles Avenue East, Suite 801, Markham, ON L3R 8T3 • 416 491-3353 • Toll Free: 1 800 563-5483 • Fax: 905 752-1540
Canadian Charitable Registration No. 10686 2949 RR0001