Overview
Late-onset Pompe disease (also called late-onset glycogen storage disease type II, late-onset acid maltase deficiency, or LOPD) is a rare inherited muscle disease caused by a shortage of an enzyme called acid alpha-glucosidase (GAA). This enzyme normally breaks down glycogen — a form of stored sugar — inside cells. When the enzyme does not work properly, glycogen builds up in muscle cells and slowly damages them over time. Unlike the severe infantile form of the disease, the late-onset version usually appears in childhood, adolescence, or adulthood, and it tends to progress more slowly. The most noticeable effects are on the muscles used for movement and breathing. People often notice increasing weakness in the legs, hips, and trunk, which can make walking, climbing stairs, or getting up from a chair difficult. The breathing muscles are also commonly affected, which can cause shortness of breath, especially when lying flat, and problems during sleep. Some people are diagnosed only after a breathing crisis or after being found to have unexplained muscle enzyme elevations on a routine blood test. The good news is that enzyme replacement therapy (ERT) with alglucosidase alfa (Myozyme/Lumizyme) has been available since 2006 and can slow the progression of muscle and breathing problems. A newer, more effective ERT called avalglucosidase alfa (Nexviazyme) was approved in 2021. These treatments do not cure the disease but can meaningfully improve quality of life and slow decline when started early. Ongoing research is exploring gene therapy and other approaches that may offer even better outcomes in the future.
Also known as:
Key symptoms:
Progressive weakness in the hips, thighs, and lower back musclesDifficulty walking, climbing stairs, or rising from a chairShortness of breath, especially when lying flatFatigue and low energy during everyday activitiesFrequent respiratory infections or pneumoniaSleep-disordered breathing or sleep apneaDifficulty swallowing in some peopleScoliosis (curved spine) in some casesElevated muscle enzymes (CK) found on blood testsMuscle pain or crampsWaddling gait or frequent fallsWeakened cough, making it hard to clear the lungs
Autosomal recessive
Passed on when both parents carry the same gene change; often skips generations
Variable
Can begin at different ages, from infancy through adulthood
FDA & Trial Timeline
3 eventsAstellas Gene Therapies — NA
Astellas Gene Therapies — PHASE1
Data sourced from FDA regulatory filings and ClinicalTrials.gov. Updated periodically.
Treatments
No FDA-approved treatments are currently listed for Glycogen storage disease due to acid maltase deficiency, late-onset.
3 clinical trialsare actively recruiting — trials can provide access to cutting-edge therapies.
View clinical trials →Specialists
View all specialists →No specialists are currently listed for Glycogen storage disease due to acid maltase deficiency, late-onset.
Treatment Centers
8 centersUniversity of Michigan
📍 Ann Arbor, Michigan
👤 Janssen Research & Development, LLC Clinicaltrial
University of Kansas Medical Center
📍 Kansas City, Kansas
Stanford University
📍 Palo Alto, California
👤 Richard Neibeger, MD
University of Pittsburgh Medical Center
📍 Pittsburgh, Pennsylvania
University of Pennsylvania
📍 Philadelphia, Pennsylvania
Harvard/MGH UDN Clinical Site ↗
Massachusetts General Hospital
📍 Boston, MA
🔬 UDNBaylor College of Medicine UDN Clinical Site ↗
Baylor College of Medicine
📍 Houston, TX
🏥 NORDStanford Medicine Rare Disease Center ↗
Stanford Medicine
📍 Stanford, CA
Travel Grants
No travel grants are currently matched to Glycogen storage disease due to acid maltase deficiency, late-onset.
Community
No community posts yet. Be the first to share your experience with Glycogen storage disease due to acid maltase deficiency, late-onset.
Start the conversation →Latest news about Glycogen storage disease due to acid maltase deficiency, late-onset
4 articlesCaregiver Resources
NORD Caregiver Resources
Support, advocacy, and financial assistance for caregivers of rare disease patients.
Mental Health Support
Rare disease caregiving can be isolating. Connect with counseling and peer support.
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.Which enzyme replacement therapy is right for me, and how soon should I start treatment?,How often should I have my lung function and muscle strength tested, and what numbers should I watch for?,Do I need breathing support at night, and how do I know when that becomes necessary?,Should my family members be tested for Pompe disease or carrier status?,Are there any clinical trials for gene therapy or new treatments that I might be eligible for?,What type of exercise or physical therapy is safe and helpful for me at this stage?,What should I do in a breathing emergency, and should I have a medical alert card or letter?
Common questions about Glycogen storage disease due to acid maltase deficiency, late-onset
What is Glycogen storage disease due to acid maltase deficiency, late-onset?
Late-onset Pompe disease (also called late-onset glycogen storage disease type II, late-onset acid maltase deficiency, or LOPD) is a rare inherited muscle disease caused by a shortage of an enzyme called acid alpha-glucosidase (GAA). This enzyme normally breaks down glycogen — a form of stored sugar — inside cells. When the enzyme does not work properly, glycogen builds up in muscle cells and slowly damages them over time. Unlike the severe infantile form of the disease, the late-onset version usually appears in childhood, adolescence, or adulthood, and it tends to progress more slowly. The m
How is Glycogen storage disease due to acid maltase deficiency, late-onset inherited?
Glycogen storage disease due to acid maltase deficiency, late-onset follows a autosomal recessive inheritance pattern. Genetic counseling can help families understand recurrence risk and testing options.
Are there clinical trials for Glycogen storage disease due to acid maltase deficiency, late-onset?
Yes — 3 recruiting clinical trials are currently listed for Glycogen storage disease due to acid maltase deficiency, late-onset on UniteRare. See the clinical trials section on this page for phase, sponsor, and site details sourced from ClinicalTrials.gov.