With many individuals with McArdle disease having tried a LCKD, this study collected patient-reported experiences, both positive and negative. 183 responses were collected from individuals with McArdle’s from 18 countries. One-third had tried a LCKD, and almost 90% experienced some degree of positive effect on activity intolerance, muscle pain, and muscle fatigue. Adverse effects were rare and generally mild to moderate. These findings underline the need for randomized clinical trials to determine if a LCKD is a suitable nutritional strategy for McArdle’s. 

Carbohydrate availability affects fat metabolism during exercise; however, the effects of complete muscle glycogen unavailability on maximal fat oxidation (MFO) rate remain unknown. Our purpose was to examine the MFO rate in patients with McArdle disease, compared to healthy controls. Despite having a much lower VO2peak, patients showed considerably higher values for the MFO rate, and for the FATmax and MFO rate-associated workload than controls. In summary, patients with McArdle disease show an exceptionally high MFO rate, which they attained at near-maximal exercise capacity. 

The Guidelines, developed by an international team of clinicians and researchers led by IamGSD, are published in Neuromuscular Disorders, the official journal of the World Muscle Society. A significant landmark in the progress of the understanding and treatment of McArdle’s and Tarui disease. Available to all free of charge under Open Access.

A randomized placebo-controlled cross-over study. An increase in KB oxidation by oral KE supplementation cannot fully compensate for the KB-induced inhibition of lipolysis and glycolysis, explaining why the drink failed to improve exercise capacity. Thus, oral KE supplementation alone cannot be recommended as treatment option for patients with GSDV.

We extensively describe phenotypic and genotypic features of a large cohort of people with McArdle disease, all attending the Highly Specialized McArdle Disease and Related Disorders service at the National Hospital for Neurology and Neurosurgery, London.

To highlight the benefits of a partnership between patient advocacy organizations (PAO) and clinical researchers in order to clinically study the prior anecdotal patient experience of utilizing a low-carbohydrate ketogenic diet (LCKD) to manage McArdle disease.

The aim of this study was to quantify fatty replacement of paraspinal and extremity muscles by magnetic resonance imaging (MRI) in a European cohort of patients with McArdle disease. The findings show that patients exhibit significant muscle fatty replacement in paraspinal muscles. This can have important implications for future management of patients.

To explore the potential of a low carbohydrate ketogenic diet (LCKD) to counter physical activity intolerance, pain and muscle damage for glycogen storage disease (GSD) V and VII, and highlight the realistic possibility that nutrition could be key.

Fourteen participants walked at a self-selected pace on a motorised treadmill for 151 min (2 hr 31 min). Six were genetically confirmed GSDV (McArdle group) and eight were pathology free individuals (Control group). Expired gas samples were collected at selected timepoints throughout and calculations of fat and carbohydrate use were made using RER. In prolonged exercise up to 121 minutes those with McArdle disease appear to use different metabolism to those without pathology. Between minute 121 and 151 the non-linear rise in fat use in the McArdle group does suggest that there is a change at c2hr that could substantiate the suggestion of a ‘Third Wind’.

In other metabolic diseases studies of Triheptanoin diet have shown that Triheptanoin increased metabolism of both fat and sugar, and had a positive effect on physical performance and reduced the level of symptoms. However, in McArdle’s the interpretation of the findings was negative: “Despite increased resting plasma malate with Triheptanoin, the increase was insufficient to generate a normal TCA turnover during exercise and the treatment has no effect on exercise capacity or oxidative metabolism in patients with McArdle disease.”

The limited prevalence of this disease translates into a global challenge of limited specialist care for patients with McArdle disease. A Centre of Expertise (CoE) represents the most expansive platform to provide patients with McArdle disease current best practice that encompass thorough assessments, accurate diagnostic methods, relevant information and guidance, multidisciplinary support and an ongoing interface between primary and specialist care.

Diagnosis of McArdle disease is frequently delayed by many years following the first presentation of symptoms to a health professional. The aim of this study was to investigate the importance of misdiagnosis in delaying diagnosis of McArdle disease.

The aim of this study was to update the main genotype and phenotype characteristics, as well as potential associations within/between them, of all Spanish individuals who are currently diagnosed with McArdle disease.

A carbohydrate-restricted diet may provide patients with McArdle disease with a consistent energy substrate for working muscles, thereby reducing the risk of muscle damage and threat of renal failure. Further research on the use of a LCKD in McArdle disease is warranted.

This study examines oxidative stress in McArdle patients and suggests future studies should evaluate a potential role for oxidative stress contributing to acute pathology (rhabdomyolysis) and possibly later onset fixed myopathy.

Review of the role of exercise in McArdle disease with the aim to better inform health-care professionals and thus better serve the interests of patients. Recommendations for regular exercise together with preexercise nutrition in children and adult patients are also provided along with examples of exercise practice and its benefits.

Carbohydrate metabolism in terms of glucose transport, glycolysis, glycogen synthesis, and glycogen breakdown in proximal and distal hind limb muscles from adult homozygous “McArdle” (PYGM p.R50X/p.R50X) and wild-type (wt/wt) mice were studied. In addition, this study compares potential changes in glucose homeostasis.

Regular physical activity attenuates the clinical severity of McArdle disease. This is quite remarkable for a monogenic disorder that consistently leads to the same metabolic defect at the muscle tissue level, that is, complete inability to use muscle glycogen stores. Further knowledge of this disorder would help patients and enhance understanding of exercise metabolism as well as exercise genomics. Indeed, McArdle disease is a paradigm of human physical activity intolerance and PYGM genotyping should be included in the genetic analyses that might be applied in the coming personalized exercise medicine as well as in future research on genetics and exercise-related phenotypes.

First-hand written narratives are a particularly valuable resource for understanding the lived experience (as opposed to the medical facts) of disease. A person with McArdle disease, a very rare disorder of muscle, wrote an account of her 32-day trek across the countryside and mountains of Wales. Her narrative is in the form of a daily diary detailing the events of each day’s walking, together with her thoughts and feelings. I present an inductive and semantic analysis of this text. Prominent themes include the alienation of having a rare disease, but also a strong sense of solidarity in the journey, and the normal pleasures and tribulations of walking the British countryside.

All patients showed a CRF below their age-/sex-matched normality value and scored clinically lower in the physical component summary and in most SF-36 domains compared with the Spanish general population. Patients showed a consistent link between higher physical HRQoL scores and higher CRF. Patients fulfilling leisure time PA recommendations showed higher CRF and physical HRQoL scores than those not meeting guideline recommendations. According to normative data for healthy subjects, CRF and physical HRQoL are severely impaired in adult patients with McArdle disease.