Neuromuscular
McArdle Disease
Also known as GSD type V, glycogen storage disease type 5, myophosphorylase deficiency
McArdle Disease is caused by bi-allelic mutations in the PYGM gene, resulting in complete absence of myophosphorylase — the muscle isoform of glycogen phosphorylase — which blocks glycogen breakdown in skeletal muscle during exercise. This
0
studies recruiting now
as of 7 Sept 2026
17
studies registered in total
as of 7 Sept 2026
0
countries with a recruiting site
as of 7 Sept 2026
None
recruiting study posted to date
among recruiting studies
Recruiting trials
No recruiting trial found right now.
17 studies are registered for McArdle Disease, but none was recruiting as of 7 Sept 2026. Here is what is still worth doing.
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About McArdle Disease
McArdle Disease is caused by bi-allelic mutations in the PYGM gene, resulting in complete absence of myophosphorylase — the muscle isoform of glycogen phosphorylase — which blocks glycogen breakdown in skeletal muscle during exercise. This leads to exercise intolerance, myalgia, and rhabdomyolysis, but the pathognomonic 'second wind' phenomenon — a spontaneous improvement in exercise capacity after 8–10 minutes — distinguishes it from other exercise-induced myopathies. Severe rhabdomyolysis can cause acute kidney injury.
Common clinical features
From Orphanet’s phenotype annotations (CC BY 4.0). Not a complete list.
Treatments being studied
3 in clinical development, from Open Targets (CC BY 4.0). Not medical advice.
Before you apply
Things trial teams commonly ask about for McArdle Disease. Not eligibility rules; those are set by each study.
- Forearm ischaemic (or non-ischaemic) exercise test showing absent venous lactate rise with normal ammonia rise is diagnostic and frequently documented as part of eligibility screening
- Genetic confirmation of bi-allelic PYGM mutations is required; the common p.R50X variant is found in approximately 60% of European alleles and can be rapidly screened
- Cardiopulmonary exercise testing (CPET) and peak VO2 are increasingly used as primary endpoints; a structured exercise test with a physiologist prior to trial application is highly recommended
Related conditions
Information, not medical advice. Trial listings are shown as recorded on ClinicalTrials.gov; whether any study is right for you is a decision for you and your clinicians, and eligibility is decided by each research team. Disease information from Orphanet (CC BY 4.0).