Symptoms vary based on the enzyme that is missing. They usually result from the buildup of glycogen or from not being able to produce glucose when needed. Because GSD occurs mainly in muscles and the liver, those areas show the most symptoms.
Symptoms may include:
- Poor growth
- Muscle cramps
- Low blood sugar
- A greatly enlarged liver
- A swollen belly
- Abnormal blood test
The age when symptoms begin and how severe they are depends on the type of GSD. Children with GSD I rarely develop cirrhosis (liver disease), but they are at an increased risk for developing liver tumors.
In some ways, GSD III is a milder version of GSD I. It also is a very rare cause of liver failure, but it may cause fibrosis (early scarring of the liver, which may be caused by a healing response to injury, infection or inflammation). GSD II is a muscle disease and does not affect the liver.
Glycogen storage disease IV causes cirrhosis; it may also cause heart or muscle dysfunction. Often, infants born with GSD IV are diagnosed with enlarged livers and failure to thrive within their first year of life. They develop cirrhosis of the liver by age 3-5.