Paroxysmal Kinesigenic Dyskinesia
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Paroxysmal kinesigenic dyskinesia (PKD) is the most common among the three typical forms of paroxysmal dyskinesia (PxD). It is defined by attacks of dystonia, chorea, or both, which are specifically triggered by sudden movements (hence kinesigenic). Infantile or childhood epilepsy may precede PKD in some instances, and hence overlap syndromes, namely, benign familial infantile seizures (BFIS) and the so-called infantile convulsion with choreoathetosis (ICCA), were recognized. Only after the discovery of the gene causing PKD, namely, PRRT2 (proline-rich transmembrane protein 2), it became evident that BFIS and ICCA were allelic conditions also caused by mutations in the same gene. Clinical syndromes have been better defined since the discovery of the PRRT2 gene for PKD, but it is clear that this is a genetically heterogeneous disorder with the PRRT2 gene accounting for up to 40–90% of cases in different studies. Phenotypes for the PRRT2 positive cases have been defined including early onset with kinesigenic triggers (but also others), multiple attacks a day, a male preponderance, and an excellent response to antiepileptic drugs, particularly carbamazepine. Phenotypic spread to include episodic ataxia and migraine, especially hemiplegic subtype, has been discovered in addition to childhood epilepsy. Other disorders where PKD-like attacks may occur include several genetic disorders, including but not limited to those associated with SCN8A (encoding a sodium voltage-gated channels alpha subunit 8), ADCY5 (encoding for adenylate cyclase 5), and SLC16A2 (encoding monocarboxylate transporter type 8 (MCT8) mutations. However, most of these have particular characteristics and are usually complex disorders with associated features. It is likely that further genetic conditions will be recognized to cause PKD.
KeywordsParoxysmal disorders Paroxysmal kinesigenic dyskinesia Paroxysmal kinesigenic dyskinesia with infantile convulsions Benign familial infantile epilepsy Hemiplegic migraine PRRT2 PKD-like episodes
A very brief dystonic attack involving the left arm is observed as soon as this lady gets ups from the chair, with no change in consciousness or associated pain, thus fulfilling the criteria for PKD (MPG 5401 kb)
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