A 14-year-old boy presented with history of multiple
daily episodes of abnormal movements of the body for the last 2 years.
The event consisted of sudden onset of uncontrollable, bizarre, twisting
movement of both arms and legs lasting for 10-30 seconds with no
impairment of consciousness. These events were often precipitated by
sudden movement. There was no family history of similar events. His
neurological examination, magnetic resonance imaging and
electroencephalography were unremarkable.
He was on six antiepileptic drugs (valproate,
levitiracetam, phenytoin, topiramate, lacosamide, clobazam) with no
reduction in frequency of these events. Home video was reviewed and
clinical possibility of paroxysmal kinesigenic dyskinesia (PKD) was
considered (Fig.1 and
Web Video 1). A homozygous single base pair
deletion (p.Arg217GlufsTer12) in exon 2 of the PRRT2 gene was
detected on Next generation sequencing. Subsequently, he was treated
with oral carbamazepine, and showed a dramatic reduction in frequency of
these events. Subsequently, all other antiepileptic drugs were tapered;
he is event-free for last 1 year on carbamazepine (10 mg/kg/day).
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Fig. 1 A still image from the video of
paroxysmal kinesigenic dyskinesia depicting abnormal twisting
movement of upper limb during the clinical event
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Primary paroxysmal kinesigenic dyskinesia (PKD) is a
hyperkinetic movement disorder characterized by recurrent, brief
(usually less than a minute) episodes of choreathetoid or dystonic
movement without alteration of consciousness. These events can be
precipitated by sudden movement; hence, the term kinesigenic. In
contrast, paroxysmal non kinesigenic dyskinesia (PNKD) is trigerred by
emotional stress, fatigue and not by sudden motor movement. PKD has
favourable prognosis with good response to treatment. Proline-rich
transmembrane protein (PRRT2) gene mutation has been implicated in
benign familial infantile epilepsy, infantile convulsions and
choreathetosis and PKD. The present case is a sporadic PRRT2
mutation-related PKD that needs wider, recognition among pediatricians.