A 6-year-old Florida boy died from malignant hyperthermia, which caused him to run a fever of 108 degrees, the Orlando Sentinel reported.

The rare genetic condition is usually triggered by anesthesia, however, Vincent Groetzner, of Mount Dora, Fla., was playing at a friend’s house when he developed the high fever and a headache. He died later at Florida Hospital Waterman in Taveres.

There are approximately 800 to 1,000 cases of malignant hyperthermia each year, according to the Malignant Hyperthermia Association, and the condition causes a sudden fever and muscle contractions.

Malignant hyperthermia is usually caused by a defective gene, but it can be triggered by high temperatures, strenuous temperatures or certain types of anesthesia. Vincent was playing outside when he suddenly could not bend his knees. A neighbor carried him home, and his mother tried to cool him down before taking him to the hospital.In the autopsy report, the medical examiner wrote that the cause of Vincent’s malignant hyperthermia was “not identified,” but added that “the child exhibited manifestations of an undiagnosed neuromuscular disorder prior to his death."

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