It is a hereditary autosomal recessive disease in which there is deficient enzyme phosphorylase (or myophosphorylase) that physically breaks down glycogen during exercise in order to ensure the energy needed for the cells, as it is the stored form of glucose in our body. It is rare and its incidence is not known. Diagnosis may be delayed as well as adult life, but symptoms are present from childhood and may have been overlooked. This disorder does not lead to disability and does not affect life expectancy.
There is severe muscular pain when starting physical exercise, which if it continues, may present severe muscle contractures. In addition, there is muscle weakness and stiffness.
These symptoms can occur in any muscle group of the body, depending on the type of physical exercise. For example, when walking the pain is related to the legs, when carrying heavy objects it concerns the upper limbs or even during chewing, it may concern the muscles in the area of the jaw.
Complications mainly involve muscular destruction that follows, and because toxic substances are released from the damaged muscle cells, patient may be led to a temporary renal insufficiency.
Blood tests are performed to determine CK enzyme, an indicator of muscle cell disruption. Previously, a muscle biopsy was performed, which was replaced by a genetic test that certainly leads to less painful diagnosis.
There is no cure, but physiotherapy provides proper guidance and learning techniques for properly practicing and maintaining physical fitness. It consists of many breaks during physical exercise, as long as there is muscle pain and avoiding intense and painful physical exercises.
For follow-up clinical trials of the disease visit: https://clinicaltrials.gov/ct2/home
- Background, Pathophysiology, Epidemiology, Genetics of Glycogen-Storage Disease Type V, March 30, 2017, http://emedicine.medscape.com/article/946577-overview
- U.S. National Library of Medicine, glycogen storage disease type V – Genetics Home Reference, https://ghr.nlm.nih.gov/condition/glycogen-storage-disease-type-v
- McArdles Disease, McArdlesDisease.org, http://mcardlesdisease.org/
- Muscular Dystrophy Association, Metabolic Diseases of Muscle – Phosphorylase deficiency (McArdle disease), January 18, 2016, https://www.mda.org/disease/metabolic-diseases-of-muscle/types/mcardle-disease.
- Muscular Dystrophy Canada, McArdle Disease, http://www.muscle.ca/about-muscular-dystrophy/types-of-neuromuscular-disorders/mcardle-disease
- N. Gordon, Glycogenosis type V or McArdle’s disease, Dev Med Child Neurol. 2003, 45, (9), p.640-644.
- G. Nogales-Gadea, R. Godfrey, A. Santalla, J. Coll-Cantí, G. Pintos-Morell, T. Pinós, J. Arenas, M.A. Martín, A. Lucia, Genes and exercise intolerance: insights from McArdle disease, Physiol Genomics, 2016, 48, (2), p.93-100.