Type V Glycogen Storage Diseases - Symptoms, Diagnosis, and Management

Introduction

Glucose is an important source of energy in one's body. It is produced from glycogen by utilizing an enzyme. Abnormalities in this enzyme are caused due to changes in the genes. When carried from the parents to the offspring, this genetic defect can result in type v glycogen storage disease. Patients suffering from this disease are usually given supportive management therapy since this condition does not have a proper treatment protocol.

What Are Glycogen Storage Diseases?

Glycogen storage diseases are genetic conditions inherited from the parents, where the offspring tend to show errors in carbohydrate metabolism. Carbohydrate metabolism requires certain enzymes to function properly. The inability of the enzymes to function adequately due to the change in genes leads to glycogen storage diseases.

What Are the Types of Glycogen Storage Diseases?

Based on the organ that is affected due to the glycogen storage disease, they are broadly divided into three types -

Glycogen storage diseases affecting the liver

• Type I

• Type III

• Type IV

• Type VI

• Type IX

Glycogen storage diseases affecting skeletal muscles.

• Type V

• Type VII

• Type X

• Type XI

• Type XII

• Type XIII

• Type XIV

Glycogen storage diseases affecting cardiac muscles.

• Type IIa

• Type IIb

• Type XV

What Is Type V Glycogen Storage Disease?

Type V glycogen storage disease is also called McArdle disease. This is because muscles utilize glucose for proper functioning. Phosphorylase is an enzyme that helps in breaking glycogen into glucose. Therefore, changes in the gene of the phosphorylase enzyme lead to a decrease in its functions, leading to type v glycogen storage disease.

What Are the Causes of Type V Glycogen Storage Disease?

It is a genetically inherited disorder that is transmitted from the parents. Therefore, both parents must possess the genes for this disease to occur in their offspring.

What Are the Symptoms of Type V Glycogen Storage Disease?

• Change in color of the urine to brownish red.

• Easy Fatigue After Any Activity - Fatigue after the first ten minutes of moderate-intensity exercise at an early age. The second wind phenomenon is when the patient feels relief after a brief rest period during exercises.

• Rabdomylosis Episodes - Continuing the skeletal muscle activity even after strenuous exercise can result in rhabdomyolysis. It is a rare lethal condition that breaks down the muscle releasing a harmful substance into the blood.

• Difficulty in mastication (chewing food).

• Dysphagia - Difficulty in swallowing.

• Muscle pain and cramps, including permanent weakness of the muscles.

What Are the Diagnostic Tools for Type V Glycogen Storage Disease?

• Good medical history.

• Clinical signs and symptoms.

• Creatine Kinase Activity Test - There is an increase in creatine kinase values in blood for about five times the normal values.

• Cycle and Walking Tests - These are physical exertion tests used to determine abnormal heart rate. The cycle tests are positive for patients with type v glucose storage disorder for the first ten minutes. Walking test setups are available only in certain hospitals.

• Blood tests to check for enzymes

• Fore Arm Exercise Test - It is a test that can specifically diagnose the condition in an easy setting.

• Molecular Genetic Testing - Target abnormal gene testing, and complete genomic testing are carried out.

• Magnetic Resonance Imaging (MRI) is a diagnostic method that utilizes a magnetic field to generate visuals of internal organs and tissue abnormalities.

What Other Evaluations Are Done Other Than Diagnostic Tests?

The following should be done to add up to the diagnosis -

• Physical examination of muscle strength.

• Genetic consultant or counselor consultation.

What Is Genetic Counselling?

It is a process in which the individuals, along with their family members, are provided with complete information about the nature of the disorder, modes of inheriting the disorder, their effects, and treatment options. This helps the family decide on a treatment approach for the patient and stay aware of the risk of getting a certain genetic disease.

What Is the Management Protocol for Type V Glycogen Storage Disease?

There is currently no treatment available for type v glycogen storage disease. Lifestyle interventions are

• Diet and exercise to control the issue.

• A diet is abundant in carbohydrates.

• Regularly working out but not over-exercising.

• Exercise supervised by professionals. Exercises are designed in a progressive manner intensifying the exercise level. There are two types of exercises:

  • Aerobic Exercise - Aerobic Exercise includes swimming, walking, jogging, and cycling. Fuel used during this kind of exercise is usually fatty acids, which are better tolerated by patients and hence can serve as a treatment.

  • Anaerobic Exercise - This type of exercise, like weight lifting, cannot be tolerated as it is intense. Glucose is released, producing energy anaerobically (without oxygen).

• Pharmacologic and Nutritional Treatments - Certain pharmacological agents and nutritional additions improve the patient's condition. These include -

  • High-dose oral ribose.

  • Verapamil.

  • Ramipril.

  • Vitamin b6.

  • Dantrolene.

  • High-dose creatine.

  • Gentamycin (intravenous).

  • Ketogenic diet.

What Is Included in the Follow-up Visits of the Patient?

A patient diagnosed with glycogen storage disease is followed up once a year for the following

• Annual physical examination.

• Annual diet review.

What Are the Exercises to Be Avoided?

Certain exercises are to be avoided and be taken care of to prevent further complications -

• Hard grip exercises cause static muscle contractions.

• High-intensity exercises.

• Exercises involving jumps and ball games.

• Avoid running, excessive swimming, and vigorous cycling.

Does Type v Glycogen Storage Disease Affect Pregnancy?

This disease does not affect pregnancy or childbirth.

What Are the Possible Complications of Glycogen Storage Disorder Type V?

• Retinal Pattern Dystrophy - Retinal metabolism requires glucose as the major substrate. Hampering of glucose leads to retinal pattern dystrophy.

• Paraspinal Wasting - Severe spinal abnormality can be identified as lower back pain.

• Acute Renal Failure - Sudden condition in which the kidneys cannot filter the blood.

• Hypertrophic Cardiomyopathy - Thickening of the heart's walls, making it difficult to pump blood.

Can Type V Glycogen Storage Disease Be Prevented?

Diseases, as such, cannot be prevented as they are genetically inherited. Getting the patient's relatives tested for glycogen storage disease is better. Prevention of disease can be done by providing an early diagnosis.

Conclusion

Type V glycogen storage disease is a rare condition that is mainly inherited. To manage glycogen storage diseases that affect the skeletal muscles, the enthusiastic attitude of clinicians, professionals in exercise, and genetics are necessary. The condition can be diagnosed using walking tests and molecular genetic testing. With proper exercise and diet modifications, glycogen storage diseases can be managed without any future complications.