Those living with diseases like Pompe disease and McArdle disease have genetic mutations which prevent their bodies from adequately breaking down glycogen, a type of complex sugar found at the cellular level. As a result, glycogen accumulates in different muscles, tissues, and organs. But what is the impact of this accumulation? Do high glycogen levels in skeletal muscles contribute to eventual muscle damage? 

According to an article in Rare Disease Advisor, researchers in Denmark are now working to determine whether glycogen accumulation could prelude muscle damage in those with Pompe disease, McArdle disease, or other glycogen storage diseases. This research will be done within a clinical trial which is currently recruiting. 

Altogether, 50 adults with one of the above conditions will enroll in the trial. Researchers are also looking for healthy individuals to enroll, most likely as controls. Within the study, the research team will use carbon-13 magnetic resonance spectroscopy to evaluate lumbar, thigh, and calf muscles. The researchers will be looking specifically at glycogen levels within these muscles to determine where levels differ between patients and controls, patients and medical literature, and muscle groups. 

What is Pompe Disease?

Pompe disease is a rare genetic disorder which can cause muscle and nerve cell damage throughout the body. GAA mutations cause Pompe disease; these mutations, as described above, prevent the body from processing glycogen. 

There are different forms of Pompe disease: classic infantile-onset, non-classic infantile-onset, and late-onset. In the classic form, symptoms typically appear within months of birth; without treatment, this form can be fatal within the first two years of life. Non-classic infantile-onset Pompe disease usually manifests around one year old; without treatment, this form can be fatal by early childhood. Finally, late-onset Pompe disease manifests between later childhood and adulthood.

Symptoms of classic infantile-onset and non-classic infantile-onset Pompe disease can (but do not always) include:

• Hypotonia (low/reduced muscle tone)
• Enlarged liver
• Progressive muscle weakness
• Poor head and neck control 
• Enlarged tongue
• Poor weight gain
• Difficulty breathing and swallowing
• Frequent lung infections
• Developmental delays
• Heart defects

Symptoms of late-onset Pompe disease can (but do not always) include:

• Progressive muscle weakness
• Joint stiffness
• An enlarged tongue that makes eating/swallowing more difficult
• Abnormal spinal curvature
• Shortness of breath and/or difficulty breathing
• Exercise intolerance