Overview
Infantile-onset Pompe disease — also called infantile-onset glycogen storage disease type II (GSD II), acid maltase deficiency, or infantile-onset acid alpha-glucosidase (GAA) deficiency — is a rare inherited metabolic disorder. It happens when the body cannot make enough of an enzyme called acid alpha-glucosidase (GAA). This enzyme normally breaks down a sugar called glycogen inside tiny cell compartments called lysosomes. When GAA is missing or not working, glycogen builds up and damages cells throughout the body, especially in the heart, muscles, and liver. Babies with the infantile form are usually diagnosed in the first few months of life. The most serious problem is a very enlarged, thickened heart (hypertrophic cardiomyopathy), which can make it hard for the heart to pump blood properly. Babies also have severe muscle weakness, poor muscle tone (called 'floppy baby' or hypotonia), difficulty feeding, and trouble breathing. Without treatment, the disease is life-threatening in the first year of life. The good news is that enzyme replacement therapy (ERT) with alglucosidase alfa (Myozyme) has been FDA-approved since 2006 and has dramatically changed outcomes for affected infants. A newer, more effective ERT called avalglucosidase alfa (Nexviazyme) was approved in 2021. Newborn screening programs in many countries now allow earlier diagnosis and faster treatment, which greatly improves survival and quality of life.
Also known as:
Key symptoms:
Severely enlarged and thickened heart (hypertrophic cardiomyopathy)Very weak muscles throughout the bodyFloppy muscle tone (hypotonia) — baby feels limp when heldDifficulty feeding and poor weight gainBreathing problems and respiratory failureEnlarged liver (hepatomegaly)Enlarged tongue (macroglossia)Delayed motor milestones — unable to hold head up or roll overRecurrent lung infections or pneumoniaRapid or labored breathingHeart failure signs such as sweating during feeding or poor color
Clinical phenotype terms (35)— hover any for plain English
Autosomal recessive
Passed on when both parents carry the same gene change; often skips generations
Infantile
Begins in infancy, roughly 1 month to 2 years old
Treatments
No FDA-approved treatments are currently listed for Glycogen storage disease due to acid maltase deficiency, infantile onset.
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Specialists
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Treatment Centers
8 centersBaylor College of Medicine Rare Disease Center ↗
Baylor College of Medicine
📍 Houston, TX
🏥 NORDStanford Medicine Rare Disease Center ↗
Stanford Medicine
📍 Stanford, CA
🔬 UDNNIH Clinical Center Undiagnosed Diseases Program ↗
National Institutes of Health
📍 Bethesda, MD
🔬 UDNUCLA UDN Clinical Site ↗
UCLA Health
📍 Los Angeles, CA
🔬 UDNBaylor College of Medicine UDN Clinical Site ↗
Baylor College of Medicine
📍 Houston, TX
🔬 UDNHarvard/MGH UDN Clinical Site ↗
Massachusetts General Hospital
📍 Boston, MA
🏥 NORDMayo Clinic Center for Individualized Medicine ↗
Mayo Clinic
📍 Rochester, MN
👤 Mayo Clinic Center for Individualized Medicine
🏥 NORDUCLA Rare Disease Day Program ↗
UCLA Health
📍 Los Angeles, CA
Travel Grants
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4 articlesCaregiver Resources
NORD Caregiver Resources
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Mental Health Support
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Family & Caregiver Grants
Financial assistance programs specifically for caregivers of rare disease patients.
Social Security Disability
Learn how rare disease patients may qualify for SSDI/SSI benefits.
Questions for your doctor
Bring these to your next appointment
- Q1.When should we start enzyme replacement therapy, and which type is best for my child?,How will we monitor whether the treatment is working, and what signs should I watch for at home?,Does my child need respiratory support now, and how might that change over time?,Are there clinical trials for gene therapy or other new treatments that my child might qualify for?,What is the risk that future children will have this condition, and is prenatal testing available?,What early intervention therapies — physical, occupational, speech — should we start right away?,What emergency plan should we have in place if my child has a breathing crisis?
Common questions about Glycogen storage disease due to acid maltase deficiency, infantile onset
What is Glycogen storage disease due to acid maltase deficiency, infantile onset?
Infantile-onset Pompe disease — also called infantile-onset glycogen storage disease type II (GSD II), acid maltase deficiency, or infantile-onset acid alpha-glucosidase (GAA) deficiency — is a rare inherited metabolic disorder. It happens when the body cannot make enough of an enzyme called acid alpha-glucosidase (GAA). This enzyme normally breaks down a sugar called glycogen inside tiny cell compartments called lysosomes. When GAA is missing or not working, glycogen builds up and damages cells throughout the body, especially in the heart, muscles, and liver. Babies with the infantile form a
How is Glycogen storage disease due to acid maltase deficiency, infantile onset inherited?
Glycogen storage disease due to acid maltase deficiency, infantile onset follows a autosomal recessive inheritance pattern. Genetic counseling can help families understand recurrence risk and testing options.
At what age does Glycogen storage disease due to acid maltase deficiency, infantile onset typically begin?
Typical onset of Glycogen storage disease due to acid maltase deficiency, infantile onset is infantile. Age of onset can vary across affected individuals.