Glycogen Storage Disease Type XV

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GSD type 15 is caused by mutations in the GYG1 gene. This gene is responsible for encoding (converting) the enzyme, glycogenin. These mutations lead to muscle weakness and cardiomyopathy (a disease of the heart muscle making it harder for the heart to pump blood to the rest of the body). 

Glycogen storage disease type 15 is an extremely rare genetic glycogen storage disorder that has only been reported in one patient to date. The estimated prevalence of the condition is less than 1 in 1,000,000.  

Clinical signs first started in childhood in the one case that has been reported and included: 

• Muscle weakness 
• Cardiac arrhythmia (irregular heartbeat) 
• Cardiomyopathy (a disease in the heart muscle that makes it harder for you heart to pump blood to the rest of the body) 
• Accumulation of abnormal storage material in the heart  
• Glycogen depletion (running out of glycogen stores) in the skeletal muscles 

A diagnosis of Glycogen Storage Disease Type 15 can be confirmed through genetic testing which will show mutations in the GYG1 gene.  

Treatment for this condition are symptomatic & supportive. They aim to manage and alleviate individual symptoms and provide support for the patient and their families.  

Glycogen storage disease type XV is an inherited condition. Humans have chromosomes made up of DNA. Genes are pieces of DNA that carry the genetic information. Each chromosome may have several thousand genes. We inherit chromosomes from the egg of the mother and sperm of the father. The genes on those chromosomes carry the instructions that determine a person’s characteristics, which are a combination of the parents.  

The pattern of inheritance of glycogen storage disease type XV is autosomal recessive. This means that carriers of the condition do not have the disorder because the other gene of this pair is working normally. Parents of children with glycogen storage disease type XV are carriers.    

When both parents are carriers, the risk to the baby in each pregnancy is  

• 25% chance (1 in 4) of developing the condition  
• 50% chance (1 in 2) for the baby to be a carrier of the condition  
• 25% chance (1 in 4) for the baby to have two working genes and neither have the condition nor be a carrier  

Genetic counselling can be requested to get a full explanation.  

For more information, please visit Association for Glycogen Storage Disease UK.

References are available on request. Please contact us on 0800 652 3181 or by emailing contact@metabolicsupport.org.

Please note calls to 0800 numbers are free from UK landlines and mobiles. Calls from business lines may be charged – please check with your provider.

This information about metabolic diseases is provided by Metabolic Support UK and is intended for educational purposes only. It should not be used for diagnostic or treatment purposes.

Should you require more detailed information please contact Metabolic Support UK by email (contact@metabolicsupport.org) or by telephone ( 0800 652 3181). For specific medical information regarding a disorder or individual please contact your GP or Paediatrician. Metabolic Support UK accepts no responsibility for any errors or omissions nor does Metabolic Support UK assume any liability of any kind for the content of any information contained within this summary or any use that you may make of it.