A gene for autosomal dominant paroxysmal choreoathetosis/spasticity (CSE) maps to the vicinity of a potassium channel gene cluster on chromosome 1p, probably within 2 cM between D1S443 and D1S197

Paroxysmal choreoathetosis/episodic ataxia is a heterogeneous neurological syndrome usually inherited in an autosomal dominant manner. Recently, the association of one form of episodic ataxia (defined by the presence of additional myokymia) with point mutations in the potassium channel gene KCNA1 was described. This gene locus on chromosome 12p (HGMW-approved symbol CSE) was excluded in a large pedigree with paroxysmal choreoathetosis and additional spasticity. Linkage to chromosome 1p where a cluster of related potassium channel genes is located, was demonstrated. Genotyping of 18 affected and 11 unaffected family members with 28 microsatellites over a region of 45 cM proved linkage with a lod score of 7.2 at a recombination fraction theta = 0 to D1S451/421/447/GGAT4C11. Crossing-over events in 9 patients and 4 unaffected offspring suggested a probable assignment of the gene to a region of 2 cM between D1S443 and D1S197.