An autosomal recessive condition characterized by recurrent myoclonic and generalized seizures, ATAXIA, slowly progressive intellectual deterioration, dysarthria, and intention tremor. Myoclonic seizures are severe and continuous, and tend to be triggered by movement, stress, and sensory stimuli. The age of onset is between 8 and 13 years, and the condition is relatively frequent in the Baltic region, especially Finland. (From Menkes, Textbook of Child Neurology, 5th ed, pp109-110)