Hyperpyrexia associated with sustained muscle contractions: an alternative diagnosis to central fever.

Muscle activity is the principal source of body heat production, and elevated core body temperatures may occur in healthy exercising persons. Hyperpyrexia from sustained tonic muscle contractions can also occur in a number of pathological conditions. The present case of hyperpyrexia associated with dystonic posturing and sustained muscle contraction in a child with encephalopathy illustrates the importance of recognizing muscular activity in the generation of fever of unknown origin following central nervous system injury. The pathophysiology, clinical features, and management of this uncommon cause of fever are discussed.