Glycogen Storage Disease, Type III (AGL)

Glycogen storage disease, type III (GSD3) is an autosomal recessive disease caused by pathogenic variants in the gene AGL. GSD3 affects the bodys ability to convert food into energy, meaning that affected individuals easily develop hypoglycemia (low blood sugar). Symptoms begin in childhood and include an enlarged liver and hypoglycemia, which must be controlled with frequent feedings. Muscle weakness begins in the 20s or 30s and ranges in severity between affected individuals. GSD3 causes the heart to become enlarged. In most patients, their enlarged heart does not cause any symptoms, but a minority of affected individuals have heart dysfunction or failure. Liver disease is progressive, and a minority of people with GSD3 experience severe liver problems such as liver dysfunction or cancer. With the exception of individuals with severe cardiac symptoms, which can be fatal, life expectancy is not reduced. It is not currently possible to predict how severe the disease will be based on the inherited variants. GSD3 may affect people of any ethnicity, but it is more common among Sephardic Jewish individuals from Morocco and those from the Faroe Islands.

For information about carrier frequency and residual risk, please see the residual risk table.