Objective: To describe the first Swedish pedigree that fits both clinical criteria for PKD and genetic confirmation for the p.Arg217Profs*8 in the PRRT2 gene.

Background: Paroxysmal Kinesigenic Dyskinesia (PKD) is triggered by initiation of voluntary movement. Episodes consist of dystonic, choreic, athetotic or ballistic movements of short duration, unilateral or bilateral with very good response to antiepileptic drugs. Familial cases are inherited in the autosomal dominant mode while secondary cases due to multiple sclerosis, vascular lesions, trauma and metabolic cause have been described. The majority of cases with PKD are caused by truncating mutations in the proline-rich transmembrane protein 2 (PRRT2) gene on chromosome 16p11.2. Several mutations in the PRRT2 gene have been originally identified as the cause of PKD in familial and sporadic cases of PKD and other paroxysmal disorders in Asians (Han Chinese, Japanese, Thai), Australians, African American and Europeans nevertheless no clear effect of a single founder has been revealed. 

Methods: Here we describe family of Swedish origin with familiar PKD. The index case is a 24-year-old right-handed man who has been suffering up to 10-15 episodes (usually 4/day) of involuntary movement affecting unilaterally the face, upper and lower extremity on the right. The episodes have been occurring since the age of 12 and last 10-15 seconds. They were usually triggered in the grounds of stress and sleep deprivation and presented in the form of athetosis precipitated by voluntary movement initiation.  Neurological examination was normal between attacks.

Family history revealed similar clinical presentation in the patient’s sister, mother and maternal grandfather. Genetic control unveiled mutation of p.Arg217Profs*8 in the PRRT2 gene in all affected members.  

Results: According to the diagnostic criteria he was diagnosed with PKD and treated with carbamazepine 150mg/d. The patient has improved and episodes were reduced to one or none/day. 

Conclusions: The phenotypic spectrum of PRRT2 associated disorders is wide and most conditions share similar paroxysmal characteristics. To our knowledge however this is the first Swedish pedigree described that fits both clinical criteria for PKD and genetic confirmation for the p.Arg217Profs*8 in the PRRT2 gene. 

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MDS Abstracts - https://www.mdsabstracts.org/abstract/a-swedish-family-with-paroxysmal-kinesigenic-dyskinesia-due-to-p-arg217profs8-truncation-in-the-proline-rich-transmembrane-protein-2-gene/