Episodic Kinesigenic Dyskinesia 2

For a general phenotypic description and a discussion of genetic heterogeneity of episodic kinesigenic dyskinesia (EKD), also referred to as paroxysmal kinesigenic choreoathetosis (PKC), see EKD1 (128200).

Clinical Features

Valente et al. (2000) reported a large Indian kindred in which 13 individuals received a definite diagnosis of PKC. Family history indicated that 4 deceased individuals had been affected. The male:female ratio was 1.8:1. Age at onset ranged from 7 to 13 years, and all had brief attacks of up to 2 minutes consisting of dystonic or choreic movements precipitated by sudden movements, with a frequency of 1 to 20 episodes per day. None of the affected patients had a history of benign infantile convulsions. However, 5 family members, including 2 with PKC, had sporadic episodes of generalized tonic-clonic seizures in their teenage years that spontaneously resolved. Incomplete (75%) penetrance was reported. Spacey et al. (2002) reported further details of the Indian family. Six patients experienced sensory aura in the form of paresthesias involving the same part of the body. Nine of 17 affected members had spontaneous remission at an average age of 23.3 years.

Mapping

By linkage and haplotype analysis of large Indian family with PKC, Valente et al. (2000) identified a 15.8-cM candidate region, referred to as EKD2, between markers D16S685 and D16S503, on chromosome 16q13-q22.1 (maximum lod score of 3.66 at D16S419). The region was distinct from and telomeric to the EKD1 locus identified in Japanese families with PKC (Tomita et al., 1999) and the ICCA locus (602066), but overlapped with a region identified in an African American family with PKC (Bennett et al., 2000). Epilepsy did not segregate with the EKD haplotype, suggesting that it is not part of the phenotype.