Skip to content
How It Works
Explore
Resources Ask a Question
Who It's For
Patients
Decode results, prep for appointments, weigh options.
Caregivers & advocates
Carry the research load for someone you love.
Providers & clinicians
Resources for patients in your practice.
Log In Ask a Question
PubMed This is a summary of 20 peer-reviewed journal articles Updated
Medical Genetics · Glycogen Storage Disease Type Ia

The Biology of GSD Ia: Genes and Metabolism

At a Glance

Glycogen Storage Disease Type Ia (GSD Ia) is caused by mutations in the G6PC gene, which prevents the liver from releasing stored sugar into the blood. This trapped sugar causes low blood sugar and dangerous buildups of lactic acid, uric acid, and triglycerides.

To manage Glycogen Storage Disease Type Ia (GSD Ia), it helps to understand what is happening at the microscopic level. The disease is caused by a “cellular traffic jam” in the liver that forces the body to change how it processes energy.

The Genetic Blueprint: The G6PC Gene

Every person has a gene called G6PC. This gene provides the instructions for making an enzyme called glucose-6-phosphatase-alpha (G6Pase-alpha) [1][2].

In GSD Ia, a child inherits two mutated copies of the G6PC gene (one from each parent), which means their body either makes very little of this enzyme or none at all [3][4]. Without this enzyme, the liver cannot perform the final step of releasing sugar into the bloodstream [5][6].

The “Locked Door” in the Liver

Think of the liver as a warehouse that stores sugar (glycogen). To get the sugar out of the warehouse and into the blood, it must go through a final “security gate” where it is turned into glucose.

  • The Problem: The G6Pase-alpha enzyme is the key to that gate [3].
  • The Result: Without the key, sugar gets stuck in the liver as a substance called glucose-6-phosphate (G6P) [7][5]. This causes the liver to swell (hepatomegaly) and leaves the rest of the body starving for energy (hypoglycemia) [6][5].

Metabolic Reprogramming: The Dangerous Detours

Because the G6P cannot exit through the normal “gate,” it begins to pile up. To deal with this backlog, the body is forced into metabolic reprogramming—it shunts the excess G6P down other biological “side roads” that were never meant to handle that much traffic [8][1].

These “detours” create metabolic byproducts that can be harmful if they reach high levels:

  1. Lactic Acid (Lactate): The excess G6P is broken down through a process called glycolysis, which creates a massive amount of lactate, leading to lactic acidosis (acidic blood) [9][10].
  2. Uric Acid: The G6P is pushed into a pathway called the “hexose monophosphate shunt.” This creates excess uric acid, which can cause joint pain or gout over time [1][11].
  3. Triglycerides (Blood Fats): The liver tries to turn the extra sugar into fat. This leads to hyperlipidemia (extremely high blood fats) and a “fatty liver” [12][13].

Confirming the Diagnosis

Because many metabolic disorders look similar on the surface, doctors use specialized genetic testing to confirm GSD Ia. Often, doctors start with a targeted “gene panel” for metabolic disorders or hypoglycemia because it is typically faster and more cost-effective [14][15]. If the panel does not provide clear answers, Whole Exome Sequencing (WES) is a powerful tool that looks at the “protein-coding” regions of all your child’s genes [16][17]. It can pinpoint the exact mutation in the G6PC gene, ending the “diagnostic odyssey” and allowing your medical team to create a management plan tailored to your child’s specific genetic profile [18][19]. Evaluation of blood levels for lactate, uric acid, and triglycerides also provides a “snapshot” of how much metabolic reprogramming is occurring [20][9].

Return to the Understanding Your Child’s GSD Ia Diagnosis.

Common questions in this guide

What causes Glycogen Storage Disease Type Ia?
GSD Ia is caused by inheriting two mutated copies of the G6PC gene, one from each parent. This mutation prevents the body from making enough of the glucose-6-phosphatase-alpha enzyme, which is required to release stored sugar from the liver into the bloodstream.
Why does GSD Ia cause high lactic acid and triglycerides?
Without the necessary enzyme, sugar gets trapped in the liver. To handle this backlog, the body redirects the trapped sugar down alternative biological pathways. This metabolic reprogramming creates excess byproducts, leading to lactic acidosis, high uric acid, and elevated blood fats.
How is a GSD Ia diagnosis confirmed?
Doctors typically use specialized genetic testing, such as a targeted gene panel or Whole Exome Sequencing, to pinpoint the exact mutation in the G6PC gene. They may also test blood levels of lactate, uric acid, and triglycerides to understand how your child's metabolism is functioning.
Why do children with GSD Ia experience low blood sugar and an enlarged liver?
Because the liver cannot release stored sugar, the rest of the body is starved for energy, resulting in low blood sugar (hypoglycemia). Meanwhile, the trapped sugar causes the liver to swell, a condition known as hepatomegaly.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.What specific mutation in the G6PC gene was found in our child's genetic testing?
  2. 2.How do our child's current levels of lactate, uric acid, and triglycerides compare to the target ranges for GSD Ia?
  3. 3.Based on this metabolic reprogramming, what are the long-term risks for our child's kidneys and liver if these levels stay high?
  4. 4.Would a Continuous Glucose Monitor (CGM) help us see how different feedings affect the 'backlog' of G6P in the liver?
  5. 5.Is there any benefit to using Whole Exome Sequencing for our other children or for future family planning?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

References

References (20)
  1. 1

    Hepatic glucose-6-phosphatase-α deficiency leads to metabolic reprogramming in glycogen storage disease type Ia.

    Cho JH, Kim GY, Mansfield BC, Chou JY

    Biochemical and biophysical research communications 2018; (498(4)):925-931 doi:10.1016/j.bbrc.2018.03.083.

    PMID: 29545180
  2. 2

    Pathogenesis of Hepatic Tumors following Gene Therapy in Murine and Canine Models of Glycogen Storage Disease.

    Kang HR, Gjorgjieva M, Smith SN, et al.

    Molecular therapy. Methods & clinical development 2019; (15()):383-391 doi:10.1016/j.omtm.2019.10.016.

    PMID: 31890731
  3. 3

    Recent development and gene therapy for glycogen storage disease type Ia.

    Chou JY, Kim GY, Cho JH

    Liver research (Beijing, China) 2017; (1(3)):174-180 doi:10.1016/j.livres.2017.12.001.

    PMID: 29576889
  4. 4

    Mutational analysis and clinical investigations of medically diagnosed GSD 1a patients from Pakistan.

    Gul B, Firasat S, Shan T, et al.

    PloS one 2023; (18(11)):e0288965 doi:10.1371/journal.pone.0288965.

    PMID: 38033126
  5. 5

    Emerging roles of autophagy in hepatic tumorigenesis and therapeutic strategies in glycogen storage disease type Ia: A review.

    Cho JH, Weinstein DA, Lee YM

    Journal of inherited metabolic disease 2021; (44(1)):118-128 doi:10.1002/jimd.12267.

    PMID: 32474930
  6. 6

    A Liver-Specific Thyromimetic, VK2809, Decreases Hepatosteatosis in Glycogen Storage Disease Type Ia.

    Zhou J, Waskowicz LR, Lim A, et al.

    Thyroid : official journal of the American Thyroid Association 2019; (29(8)):1158-1167 doi:10.1089/thy.2019.0007.

    PMID: 31337282
  7. 7

    Bezafibrate induces autophagy and improves hepatic lipid metabolism in glycogen storage disease type Ia.

    Waskowicz LR, Zhou J, Landau DJ, et al.

    Human molecular genetics 2019; (28(1)):143-154 doi:10.1093/hmg/ddy343.

    PMID: 30256948
  8. 8

    A patient with glycogen storage disease type IA combined with hepatic adenoma: A case report.

    Yin M, Chang L, Jiang P, et al.

    Genes & diseases 2023; (10(3)):701-704 doi:10.1016/j.gendis.2022.08.002.

    PMID: 37396534
  9. 9

    Severe perioperative lactic acidosis in a pediatric patient with glycogen storage disease type Ia: a case report.

    Takahashi T, Oue K, Imado E, et al.

    JA clinical reports 2023; (9(1)):91 doi:10.1186/s40981-023-00683-z.

    PMID: 38114842
  10. 10

    Glucose-6 Phosphate, A Central Hub for Liver Carbohydrate Metabolism.

    Rajas F, Gautier-Stein A, Mithieux G

    Metabolites 2019; (9(12)) doi:10.3390/metabo9120282.

    PMID: 31756997
  11. 11

    Clinical features of gout in adult patients with type Ia glycogen storage disease: a single-centre retrospective study and a review of literature.

    Xu N, Han X, Zhang Y, et al.

    Arthritis research & therapy 2022; (24(1)):58 doi:10.1186/s13075-021-02706-5.

    PMID: 35219330
  12. 12

    Impaired Very-Low-Density Lipoprotein catabolism links hypoglycemia to hypertriglyceridemia in Glycogen Storage Disease type Ia.

    Hoogerland JA, Peeks F, Hijmans BS, et al.

    Journal of inherited metabolic disease 2021; (44(4)):879-892 doi:10.1002/jimd.12380.

    PMID: 33739445
  13. 13

    Serum sex hormone-binding globulin levels are reduced and inversely associated with intrahepatic lipid content and saturated fatty acid fraction in adult patients with glycogen storage disease type 1a.

    Simons PIHG, Valkenburg O, Telgenkamp I, et al.

    Journal of endocrinological investigation 2022; (45(6)):1227-1234 doi:10.1007/s40618-022-01753-2.

    PMID: 35132570
  14. 14

    Case Report: Glycogen Storage Disease Type Ia in a Chinese Child Treated With Growth Hormone.

    Wu S, Guo S, Fu L, et al.

    Frontiers in pediatrics 2022; (10()):921323 doi:10.3389/fped.2022.921323.

    PMID: 35783312
  15. 15

    Glycogen Storage Disease type IA refractory to cornstarch: Can next generation sequencing offer a solution?

    Steg Saban O, Pode-Shakked B, Abu-Libdeh B, et al.

    European journal of medical genetics 2022; (65(6)):104518 doi:10.1016/j.ejmg.2022.104518.

    PMID: 35550444
  16. 16

    [Exome diagnostics in neurology].

    Zech M, Wagner M, Schormair B, et al.

    Der Nervenarzt 2019; (90(2)):131-137 doi:10.1007/s00115-018-0667-1.

    PMID: 30645660
  17. 17

    The application of whole-exome sequencing in the early diagnosis of rare genetic diseases in children: a study from Southeastern China.

    Lai G, Gu Q, Lai Z, et al.

    Frontiers in pediatrics 2024; (12()):1448895 doi:10.3389/fped.2024.1448895.

    PMID: 39439447
  18. 18

    Targeted exome sequencing identified a novel frameshift variant in the PGAM2 gene causing glycogen storage disease type X.

    Nayab A, Alam Q, Alzahrani OR, et al.

    European journal of medical genetics 2021; (64(9)):104283 doi:10.1016/j.ejmg.2021.104283.

    PMID: 34237446
  19. 19

    Genetic Studies of Tic Disorders and Tourette Syndrome.

    Qi Y, Zheng Y, Li Z, et al.

    Methods in molecular biology (Clifton, N.J.) 2019; (2011()):547-571 doi:10.1007/978-1-4939-9554-7_32.

    PMID: 31273721
  20. 20

    Successful treatment of diabetes associated with glycogen storage disease type Ia.

    Yuan X, Ma W, Wu X, et al.

    Diabetic medicine : a journal of the British Diabetic Association 2021; (38(2)):e14373 doi:10.1111/dme.14373.

    PMID: 32740965

This page explains the biology and genetics of GSD Ia for educational purposes only. Always consult your pediatric metabolic specialist or geneticist for questions about your child's specific condition and lab results.

Get notified when new evidence is published on Glycogen storage disease due to glucose-6-phosphatase deficiency type Ia.

We monitor PubMed for new peer-reviewed studies on this topic and email a short summary when something meaningful changes.