16p11.2-RELATED PAROXYSMAL KINESIGENIC DYSKINESIA AND DOPA-RESPONSIVE PARKINSONISM IN A CHILD

Paroxysmal kinesigenic dyskinesia (PKD) is a rare, episodic movement disorder of unknown cause that is defined by short duration of motor attacks lasting less than 1 minute without pain or alteration in consciousness, age at onset between 1 and 20 years, control with carbamazepine or phenytoin, no identifiable underlying cause, and a normal neurologic examination.1 The constellation of tremor, bradykinesia, cogwheeling, and cognitive dysfunction that comprises parkinsonism is not a typical feature of PKD. In a large cohort of patients with PKD, one atypical patient (with age at onset of 53 years) was treated with levodopa and was subsequently diagnosed with likely PD.1 PKD has been mapped to the pericentromeric region of chromosome 16p11.2. However, no genetic mutation has been identified.1–3 We report a child with PKD who developed juvenile-onset dopa-responsive parkinsonism and was found to have a microdeletion at 16p11.2. ### Case report. A 17-year-old boy with a history of carbamazepine-responsive adventitious limb movements diagnosed by one of the authors (M.J.R.), possible infantile-onset convulsions, and verbal learning disabilities presented with acute-onset gait ataxia. Therapy with carbamazepine continues as attempts to wean the medication over the first few years of life resulted in recurrence of brief attacks of spontaneous, jerking, limb movements exacerbated by movement …