[A child with paroxysmal exertion-induced dyskinesia]

We experienced a 12-year-old boy with paroxysmal exertion (exercise)-induced dyskinesia (PED). His attacks, characterized by painless paralytic stiffness of the extremities during running or playing, developed at 4 years of age. He was initially diagnosed as having epilepsy based on epileptic discharges on interictal EEG. Although several anti-epileptic drugs were not effective, clorazepate was found to be very useful for complete control of attacks for 3 years. His attacks recurred at 8 years of age and appeared to be aggravated by psychological stress, fatigue and lack of sleep. His attacks were confirmed to be non-epileptic paroxysmal hypokinesia with rigid tetraplegia, by ictal video EEG recording, and he was diagnosed as having PED. They did not respond to various anti-epileptic drugs and L-dopa/carbidopa. His attacks were reduced to some extent by administration of hydroxyzine. PED is a very rare condition and similar to paroxysmal kinesigenic dyskinesia (PKD). There is a strong possibility that patients with PED have been misdiagnosed as PKD.