Heat stroke - least common of the heat illnesses but almost always fatal unless promptly recognized and treated. The urban, elderly poor are the most common victims of heat stroke. Classic - occurs after several days of temperatures above 37.0 C or somewhat lower temperatures but with high relative humidity. Active perspiration is continuous but eventually fails and body temperature rises sharply. The first symptom may be sudden collapse.
Muscle cramps are unusual.
Patients progress to coma. Hot and dry skin is usual but sweating may persist. Exertional - seen in association with events that increase endogenous heat production. In the U.S. the majority of cases occur in competitive long distance runners, football players and military recruits. Sustained physical exertion commonly precedes heat stroke.