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PubMed This is a summary of 20 peer-reviewed journal articles Updated
Endocrinology · Glycogen Storage Disease Type I

GSD Ia vs GSD Ib: Understanding the Differences

At a Glance

Glycogen Storage Disease Type I is divided into two main subtypes. GSD Ia primarily affects the liver and kidneys, while GSD Ib also causes immune system dysfunction and digestive issues like IBD. Both require cornstarch therapy, but GSD Ib may also be treated with Empagliflozin for immune support.

While all types of Glycogen Storage Disease Type I (GSD I) involve the same basic “broken switch” for blood sugar, the condition is divided into two main subtypes based on which part of that switch is affected. Understanding your child’s specific subtype is essential because it determines their long-term care plan and which specialists they will need to see.

The Subtype Matrix

Both subtypes are rare, but they differ in their genetic cause and the symptoms they produce beyond blood sugar management.

  • GSD Ia (von Gierke Disease): Caused by mutations in the G6PC1 gene [1]. Accounts for approximately 80% of GSD I cases [2]. Primarily liver and kidney focused [3].
  • GSD Ib: Caused by mutations in the SLC37A4 gene [4]. Accounts for approximately 20% of GSD I cases [2]. Involves immune system dysfunction and gastrointestinal issues [5][6].

GSD Ib: The Immune Component

For families with GSD Ib, the “broken switch” affects more than just the liver. It also affects neutrophils, which are a critical type of white blood cell that fights bacterial infections [5].

  • Neutropenia: This is a condition where the body has a dangerously low number of neutrophils [5].
  • Neutrophil Dysfunction: Even the white blood cells the body does produce often do not work correctly. They have trouble moving to the site of an infection or “eating” bacteria effectively [7][8].
  • Common Symptoms: Children with GSD Ib are prone to recurrent bacterial infections, particularly of the skin and ears, as well as painful oral ulcers (mouth sores). There is also a risk for gum disease (periodontitis), which is closely monitored and actively managed by your dental and medical care team [9][10].
  • Inflammatory Bowel Disease (IBD): Up to 70-80% of patients with GSD Ib develop symptoms similar to Crohn’s disease, including chronic diarrhea, abdominal pain, and intestinal inflammation [6][11].

The Empagliflozin Breakthrough

Until recently, the main treatment for the immune issues in GSD Ib was a medication called G-CSF, which stimulates the bone marrow to make more white blood cells [12]. However, a major breakthrough has occurred with the “repurposing” of a drug called Empagliflozin [13].

Originally designed for diabetes, Empagliflozin has been found to be highly effective for GSD Ib [14]. In GSD Ib, a toxic “look-alike” sugar called 1,5-anhydroglucitol-6-phosphate (1,5-AG6P) builds up inside neutrophils and poisons them [15][16]. Empagliflozin helps the kidneys flush this toxin out of the body through the urine [17].

  • Results: Many patients taking Empagliflozin see their white blood cell counts rise, their mouth sores disappear, and their IBD symptoms improve significantly [18][19].

Summary of Care

Regardless of the subtype, the “gold standard” of care remains strict dietary management with cornstarch to prevent hypoglycemia [20]. However, families with GSD Ib will work more closely with immunologists and gastroenterologists to manage the additional risks to the immune system and the digestive tract [5][6].

Common questions in this guide

What is the main difference between GSD Ia and GSD Ib?
While both types affect blood sugar regulation, GSD Ia primarily impacts the liver and kidneys. GSD Ib also causes immune system dysfunction, low white blood cell counts, and gastrointestinal issues like inflammatory bowel disease.
Why do children with GSD Ib get frequent skin and ear infections?
GSD Ib causes a condition called neutropenia, meaning the body has dangerously low numbers of white blood cells. Furthermore, the white blood cells that are produced often do not work correctly, making it much harder to fight off bacterial infections.
How does Empagliflozin help treat GSD Ib?
Empagliflozin helps the kidneys flush out a toxic sugar byproduct that builds up inside and poisons white blood cells in GSD Ib patients. This treatment can increase healthy white blood cell counts, heal mouth sores, and significantly improve intestinal symptoms.
What causes Inflammatory Bowel Disease (IBD) in GSD Ib patients?
The immune system dysfunction seen in GSD Ib can lead to intestinal inflammation that is very similar to Crohn's disease. Up to 80% of patients with GSD Ib experience symptoms like chronic diarrhea and abdominal pain.
Do both GSD Ia and GSD Ib require cornstarch therapy?
Yes, strict dietary management with cornstarch remains the gold standard of care for both GSD Ia and GSD Ib. It is required to maintain normal blood sugar levels and prevent dangerous hypoglycemia.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Based on our child's subtype, should we be monitoring their absolute neutrophil count (ANC) regularly?
  2. 2.Are we seeing any early signs of inflammatory bowel disease (IBD), such as chronic diarrhea or mouth sores?
  3. 3.Is our child a candidate for Empagliflozin, and how would it change their current medication or feeding schedule?
  4. 4.If our child is starting Empagliflozin, how often do we need to monitor their 1,5-anhydroglucitol (1,5-AG) levels?
  5. 5.Does the GSD Ib diagnosis change our child's vaccination schedule or how we handle minor infections?

Questions For You

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References

References (20)
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    The role of glucose-6-phosphatase activity in glucose homeostasis and its potential for diabetes therapy.

    Tan LS, Lau HH, Abdelalim EM, et al.

    Trends in molecular medicine 2025; (31(2)):152-164 doi:10.1016/j.molmed.2024.09.005.

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    Genetic characterization of GSD I in Serbian population revealed unexpectedly high incidence of GSD Ib and 3 novel SLC37A4 variants.

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This page explains the differences between GSD Ia and GSD Ib for educational purposes only. Always consult your pediatric endocrinologist and medical team regarding your child's specific diagnosis and comprehensive care plan.

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