Mechanisms of rhabdomyolysis

Rhabdomyolysis is a common disorder that occurs as a primary disease or as a complication of a broad spectrum of other diseases. Although some cases are caused by hereditary metabolic or structural abnormalities of the skeletal muscle cell, the majority of cases occur in healthy persons as a result of exhaustive exercise, infections, intoxications, deficiency states, or trauma. Although the causes of rhabdomyolysis are diverse, current evidence suggests that there may be a common final pathway that mediates cellular injury. Thus some noxious factor, perhaps a drug that injures the plasma membrane of the cell, a toxin that activates a cytolytic enzyme, a factor that interferes with metabolism and disrupts the integrity of the skeletal muscle cell, a cytokine such as tumor necrosis factor, or simple hypoxia that reduces energy production by the cell, serves to increase cellular permeability to sodium ions. When sodium ions accumulate in the cytoplasm of the cell, an increase of cytosolic or mitochondrial calcium follows. Calcium activates a variety of proteolytic enzymes that injure the cell membrane, allowing efflux of cellular components into the circulation. The ability to identify some of these components, such as myoglobin or creatine kinase, facilitates clinical recognition of rhabdomyolysis. The cytosolic components released into the circulation, under appropriate conditions, may be life threatening, eg, release of potassium causes hyperkalemic cardiotoxicity. In this review, I attempt to describe a variety of factors that are known to be injurious to skeletal muscle cells and, when possible, describe the apparent mechanism whereby these factors result in injury and disruption of the muscle cell.