Vall d'Hebron University Hospital in Barcelona, Hospital 12 de Octubre in Madrid and Hospital Meixoeiro in Vigo have carried out the first Spanish Registry of patients with McArdle’s rare disease.McArdle's disease, or type V glycogen storage, is a disorder of the metabolism of carbohydrates that prevents obtaining energy from the reserves of sugar as glycogen located in the muscles. For those affected, this causes intolerance to exercise, fatigue and cramps when performing simple activities such as climbing stairs or lifting weights.The registry collects data from 239 patients (ages 9 to 93) diagnosed in the NHS and is the largest world series studied for this disease.The work results allowed to set a new rate of disease prevalence (0.6 per 100,000 inhabitants), to study characteristics unknown before and to demonstrate that presently -and in most cases- McArdle's disease can be detected in pediatric or adolescent patients by means of molecular genetic studies from a blood sample, without having to perform a muscle biopsy.At the same time, the Neuromuscular and Mitochondrial Pathology group at Vall d'Hebron Research Institute (VHIR), led by Dr. Ramon Martí and Dr. Antoni Andreu, has developed an animal model of genetically modified mice that reproduces accurately the symptoms of diseases caused by faults in the storage of glycogen, such as McArdle's disease. The work findings, published in Brain, will presumably mean, beyond the animal model, a change of trend in the study of neuromuscular diseases, such as Duchenne's muscular distrofia or diseases with which McArdle shares the type of mutation, such as the Cystic Fibrosis.                Until now there was a shortage of valid and standardized  trial models allowing to develop restoration therapies of the activity of the enzymes that are missing in these alterations. The glucose is stored in the organs as glycogen forming a few reserve chains. When an energetic demand happens, especially in the muscle, this glucose must be mobilized, and it is necessary to transform again glycogen into glucose. Glycogen phosphorylase or myophosphorylase is the enzyme that separates the molecules of glucose from the chain of glycogen, acting as scissors that break again glycogen into molecules of glucose to facilitate that the rest of organs, mainly the muscle, may have it for its metabolic activity. McArdle's disease is a type of muscular glicogenosis disease, considered as a rare disease in which this myophosphorylase enzyme is absent due to a fault in the genetic codification.