McArdle Disease: A Diagnostic Challenge Due to Nonspecific Clinical Manifestations

McArdle disease is a rare myopathy caused by hereditary myophosphorylase deficiency. It presents nonspecific symptoms, such as intolerance to physical exercise, early fatigue, and myalgias, and represents a paradigmatic example of one of the main challenges in clinical practice: the recognition of nonspecific and common symptoms as clinically relevant manifestations of rare diseases. The nonspecificity of symptoms leads to a frequent delay from the onset of first clinical signs to diagnosis. We present a case of McArdle disease diagnosed in a Portuguese adult patient. We believe this report will highlight the need to enhance knowledge and awareness about this rare pathology to diagnose and manage these patients promptly.