PRRT2 mutation in Korean patients with paroxysmal kinesigenic dyskinesia: A clinico-genetic analysis

Background & Objective: Recently, mutations in PRRT2 have been found to cause paroxysmal kinesigenic dyskinesia (PKD). However, only several reports have described the detailed clinical features of patients with the PRRT2 mutation compared to those without the mutation. Furthermore, 16p11.2 microdeletions including PRRT2 also have been reported in patients with PKD; however, it is unknown to what extent the PRRT2 deletion contributes to the development of PKD. Methods: We performed mutation screening in 29 Korean patients with PKD analyzing the sequence and gene dosage of PRRT2 and their clinical features.

Results: Overall, genetic abnormalities in PRRT2 were identified in 7 patients (24%): 3 from the 6 familial cases (50%) and 4 from the 23 sporadic cases (17%). The previously reported c.649dupC and c.649delC were found in 5 and 1 patient, respectively, and a novel mutation c.323_324delCA was found in 1 patient. No patients had deletions involving the PRRT2 gene. Compared with the mutation-negative cases, the age of PKD onset was earlier in the mutation-positive cases. However, there were no differences in the other clinical features. A dystonia-only phenotype was reported only in the mutation-negative cases. Contrary to common belief that patients with PKD have an excellent response to carbamazepine, 3 mutation-positive patients taking carbamazepine reported only a partial response.

Conclusions: PRRT2 is a common causative gene for Korean patients with PKD. Our results show that the incomplete response to carbamazepine does not exclude the PRRT2 mutation.