Everyone experiences the disease differently. Symptoms can range from mild and manageable to severe and life-threatening.
Our bodies make, store and access energy. We convert the foods we eat into a simple sugar called glucose. If we have more glucose than we need, these molecules join together to form glycogen which can be stored in our muscles.
When we need energy, an enzyme called phosphorylase (or myophosphorylase) breaks down the stored glycogen. People with McArdle disease have inactive phosphorylase, so their muscles cannot access the stored glycogen. Without the energy they need, muscles cramp and fatigue during exercise.