A rare paroxysmal movement disorder, with childhood or adolescent onset, characterized by paroxysmal choreiform, dystonic, and myoclonic movements involving the limbs (mostly distal upper limbs), neck and/or face, which can progressively increase in both frequency and severity until they become nearly constant. Patients may also present with delayed motor milestones, perioral and periorbital dyskinesias, dysarthria, hypotonia, and weakness.