Glycogen storage disease type 1 is an inherited disorder caused by the buildup of a complex sugar called glycogen in the body's cells. The accumulation of glycogen in certain organs and tissues, especially the liver, kidneys, and small intestines, impairs their ability to function normally. Researchers have described two types of glycogen storage disease type 1, which differ in their signs and symptoms and genetic cause. These types are known as glycogen storage disease type IA and glycogen storage disease type IB.
Glycogen storage disease type 1A is characterized by growth retardation leading to short stature and accumulation of glycogen and fat in the liver and kidneys. Although some newborns present with severe hypoglycemia, it is more common for infants to present at age three to four months with hepatomegaly, lactic acidosis, hyperuricemia, hyperlipidemia, and/or hypoglycemic seizures. Untreated children typically have doll-like faces with fat cheeks and relatively thin extremities. Xanthoma and diarrhea may be present. Impaired platelet function can lead to a bleeding tendency, making epistaxis a frequent problem. Glycogen storage disease type 1A is caused by the deficiency of glucose-6-phosphatase (G6Pase) catalytic activity which results from mutations in the G6PC gene. This condition is inherited in an autosomal recessive pattern. Source: Genetic and Rare Diseases Information Center (GARD), supported by ORDR-NCATS and NHGRI.