Modified Ketogenic Diet in Patients With McArdle Disease Part B

Inclusion Criteria: * Genetically confirmed GSDV * Patient is willing and able to provide written informed consent prior to participation. * Patient is ambulatory. * Women in fertile age must be willing to practice the following medically acceptable methods of birth control Exclusion Criteria: * Patient has any prior or current medical conditions that, in the judgment of the Investigator, would prevent the patient from safely participating in and/or completing all study requirements. * Pregnancy or breastfeeding * Patient does not have the cognitive capacity to understand/comprehend and complete all study assessments * Patients with porphyria or disorders of fat metabolism (primary carnitine deficiency, carnitine palmitoyltransferase I or II, β-oxidation defects etc.).