Paroxysmal dyskinesia

Paroxysmal dyskinesia (PxD) is a group of rare movement disorders characterized by episodic, involuntary movements that may include dystonia (sustained muscle contractions causing abnormal postures), chorea (irregular, flowing movements), athetosis (slow, writhing movements), or ballism (large-amplitude flinging movements). Between episodes, neurological examination is typically normal. The condition primarily affects the motor system, with episodes varying in duration, frequency, and triggers depending on the specific subtype. Three major subtypes are recognized: paroxysmal kinesigenic dyskinesia (PKD), paroxysmal nonkinesigenic dyskinesia (PNKD), and paroxysmal exercise-induced dyskinesia (PED). PKD is triggered by sudden voluntary movements and typically has brief episodes lasting seconds to minutes. PNKD is triggered by stress, caffeine, alcohol, or fatigue, with episodes lasting minutes to hours. PED is triggered by prolonged physical exertion, with episodes lasting minutes to hours. PKD is associated with mutations in the PRRT2 gene, PNKD with mutations in the PNKD (MR-1) gene, and PED with mutations in the SLC2A1 gene (encoding the GLUT1 glucose transporter), among others. Treatment varies by subtype. PKD typically responds well to low-dose anticonvulsants, particularly carbamazepine or oxcarbazepine, often with dramatic improvement. PNKD is generally managed by avoidance of known triggers, with benzodiazepines such as clonazepam sometimes used. PED associated with GLUT1 deficiency may benefit from a ketogenic diet. The prognosis is generally favorable, particularly for PKD, where episodes may decrease in frequency with age. Genetic testing is important for confirming the diagnosis and guiding appropriate management.

Data sourced from FDA regulatory filings and ClinicalTrials.gov. Updated periodically.

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