A rare disorder characterized by early-onset progressive encephalopathy with migrant, continuous myoclonus. Three cases have been reported. The focal continuous myoclonus appeared during the first months of life. Prolonged bilateral myoclonic seizures and generalized tonic-clonic seizures occurred later. Subsequently, a progressive encephalopathy with hypotonia and ataxia appeared. Cortical atrophy was revealed by computed tomography (CT) scan and magnetic resonance imaging (MRI). The aetiology is unknown.