Metabolic myopathies series part 1: What we need to know

ABSTRACT Metabolic myopathies, a group of genetic disorders characterized by disruptions in muscle cell pathways, often lead to significant muscle fatigue. The potential underdiagnosis of these conditions is a concern because it can lead to long-term complications. Nurse practitioners are in a prime position to identify and refer these patients, thereby preventing such sequelae. Three genetic disorders affecting muscle metabolism include McArdle disease, Tarui disease, and carnitine palmitoyltransferase II deficiency. McArdle disease is a glycogen storage disease caused by a flaw in the production of a critical muscle enzyme called phosphorylase, leading to the inability to break down glycogen within muscle cells. Muscle pain, fatigue, and sometimes rhabdomyolysis can result. Tarui disease results from insufficient phosphofructokinase, which disrupts glycolysis, leading to exercise intolerance. Carnitine palmitoyltransferase II deficiency affects lipid metabolism, disturbing long-chain fatty acid (LCFA) transport into the mitochondria. The mitochondria use these LCFAs to produce energy. Disruption can lead to exertional muscle pain and myoglobinuria.