For the 2023 Image Competition, the ACR sought images representing a diverse range of patients with idiopathic inflammatory myopathies (IIMs) or IIM mimics. These images won the Europe and Central Asia region.
Glycogen Storage Disease Type V Diagnosed Using Imaging, Biopsy & Genetic Testing
These images depict a 55-year-old patient with suspected polymyositis who presented with limb weakness, elevated creatine phosphokinase levels (>3,000 IU/L) and myopathic findings on electromyography. Magnetic resonance imaging of the thigh muscle revealed predominant diffuse fat replacement in the quadriceps and hamstring muscles (red arrows) and scattered muscle edema (red arrowhead). Autoimmunity tests were negative. Deltoid muscle biopsy showed vacuoles on trichrome staining (Gomori stain), positive periodic acid-Schiff (PAS) accumulation and subsarcolemmal cytochrome C oxidase (COX) staining. The absence of myophosphorylase activity in the muscle biopsy, along with confirmation through genetic testing, established a diagnosis of glycogen storage disease type V (i.e., McArdle disease).
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The most common disorder of glycogen metabolism is also the most common metabolic myopathy overall: McArdle disease (GSD-V), whose prevalence is approximately one in 40,000. Learn more in our article, “Tips for Diagnosing Metabolic Myopathies.”
Marco Fornaro, MD, is a researcher in rheumatology at the University of Bari, Italy. His focus is on idiopathic inflammatory myopathies, a group of diverse systemic diseases that often require differential diagnosis from other myopathies.
