Painful Myopathies–Metabolism of Muscle Cells and Metabolic Myopathies

SUMMARY

Myalgias may be caused by intrinsic muscular factors [inflammation, mechanical disturbances, ischemia, metabolic abnormalities, membrane alterations] or by extrinsic factors like diseases of the peripheral or central nervous system. Primary metabolic myopathies are mostly caused by disturbances of energy metabolism. Usually these patients present with exercise-induced myalgia, which is commonly associated with muscle weakness. If rhabdomyolysis occurs further thorough investigations for a metabolic myopathy are mandatory. The pathogenesis of myalgia is thought to be related to certain biochemical mediators. Disturbances of anaerobic and aerobic muscle metabolism are typical for metabolic myopathies causing myalgia. These disorders are due to enzyme malfunction in the following pathways: glycogenolysis, glycolysis, β-oxidation of fatty acids, and the respiratory chain. Treatment of metabolic myopathies is limited. Non-specific measures include physiotherapy, non-steroidal analgesics, chinine, and L-carnitine. It is essential, however, to avoid endurance exercise with abnormalities of aerobic metabolism and to avoid brief intensive exercise with disturbances of anaerobic metabolism.

KEYWORDS:

• Myalgia
• etiology
• metabolic myopathy
• metabolism