Presentation and Diagnosis

Infants with GSDIa present with fasting hypoglycemia, hepatomegaly, and biochemical and clinical abnormalities1

During the first few months of life, infants with GSDIa often remain asymptomatic, as frequent feedings provide adequate glucose to prevent hypoglycemia.1 Symptoms of GSDIa typically start to emerge between 3 to 6 months of age, as the interval between feedings increases.1

Signs and Symptoms - Hypoglycemia, Signs and Symptoms - Hepatomegaly, Signs and Symptoms – Biochemical Abnormalities, Additional symptoms seen in older infants

Genetic testing typically confirms a GSDIa diagnosis1

No newborn screening available for GSDIa

No newborn screening currently available for GSDIa4

Molecular genetic testing typically confirms diagnosis of GSDIa

Identification of pathogenic variants in the G6PC (G6PC1) gene via molecular genetic testing typically confirms diagnosis5

Liver biopsy may be performed if genetic testing inconclusive

If genetic testing is inconclusive, liver biopsy may be performed to determine G6Pase activity5

Early diagnosis of GSDIa is critical

Early diagnosis of GSDIa is critical to reduce the risk of life-threatening hypoglycemia and long-term complications1,2

Learn about GSDIa progression
Signs and Symptoms - Hypoglycemia, Signs and Symptoms - Hepatomegaly, Signs and Symptoms – Biochemical Abnormalities, Additional symptoms seen in older infants

Abbreviations: G6Pase, glucose-6-phosphatase; GSDIa, glycogen storage disease type Ia.

References: 1. Kishnani PS, Austin SL, Abdenur JE, et al. Diagnosis and management of glycogen storage disease type I: a practice guideline of the American College of Medical Genetics and Genomics. Genet Med. 2014;16(11):e1. 2. Derks TGJ, Rodriguez-Buritica DF, Ahmad A, et al. Glycogen storage disease type Ia: current management options, burden and unmet need. Nutrients. 2021;13(11):3828. 3. Özen H. Glycogen storage diseases: new perspectives. World J Gastroenterol. 2007;13(18):2541-2553. 4. HRSA. Recommended uniform screening panel. Accessed August 1, 2025. hrsa.gov/advisory-committees/heritable-disorders/rusp 5. Bali DS, El-Gharbawy A, Austin S, et al. Glycogen storage disease type I. 2006. In: Adam MP, Feldman J, Mirzaa GM, et al, eds. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2024. Accessed June 27, 2025. https://www.ncbi.nlm.nih.gov/books/NBK1312/

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