A 2-year study, published today in The New England Journal of Medicine, details the first viable treatment for McArdle's disease, a muscle disorder first defined in the 1950s that results from a deficiency of an enzyme that breaks down muscle glycogen a stored form of carbohydrate that has long been recognized to be an important anaerobic fuel. Less well recognized is the fact that glycogen is also critical for normal oxidative metabolism.
"When there is no glycogen available, as is the case in McArdle's disease, patients have a very low oxidative capacity and rapidly fatigue with modest exercise such as walking up a slight incline," said Dr. Ronald Haller, a professor of neurology and internal medicine at UT Southwestern, staff physician at the North Texas Veterans Affairs Health Care System and senior author of the paper.
"By using an oral source of glucose the equivalent of a soft drink we show in this study that these patients are able to undertake exercise more easily, especially in the first eight to 10 minutes of physical activity. That's important because it's in that period that they are particularly vulnerable to muscle injury."
Dr. Haller, who developed and directs the Neuromuscular Center at the Institute for Exercise and Environmental Medicine at Presbyterian Hospital, said a conservative estimate of the prevalence of McArdle's disease is one case in every 100,000 people.
"These patients appear normal their main problem is exercise intolerance," Dr. Haller said. "Often, they are told by physicians that they are simply out of shape or not trying hard enough. It's e
Contact: Rachel Horton
UT Southwestern Medical Center