Heat stroke-like episode in a child caused by zonisamide

A 2-year-old mentally retarded boy with frontal lobe epilepsy presented with an episode that resembled heat stroke during the administration of zonisamide. He developed hyperpyrexia with oligohidrosis and central neurological symptoms, including, chorea-like involuntary movements, resting tremor, and cogwheel rigidity. A sweat test using pilocarpine iontophoresis revealed a marked reduction in the sweat response, which suggested a postganglionic sweating dysfunction. A skin biopsy examined by light and electron microscopy showed no morphological abnormality in the sweat glands. The oligohidrosis caused by zonisamide was reversible in that the patient regained the ability to sweat within 2 weeks of the cessation of drug administration. Children receiving zonisamide should be monitored for oligohidrosis and the development of neurological symptoms associated with an elevation of body temperature.