The Case of a Not So Wimpy Patient

McArdle disease, also known as glycogen storage disease V (GSD V), is a pure myopathy of glycogen utilization caused by inherited mutations in both alleles ofthe PYGM gene, which encodes myophosphorylase. This disorder usually presents in younger patients with symptoms of exercise intolerance, exercise-associated myalgias and cramping, or recurrent myoglobinuria (1). Here we describe the case of a 39-year-old woman with McArdle disease who had a lifelong history of exercise intolerance and fatigability that she thought was just her being “wimpy” at the start of exertion and her pain was normal. This patient presented to our clinic for answers following repeated episodes of myoglobinuria. In this case study, we report on the pathophysiology of McArdle disease, the diagnostic workup, and management options available for patients.