Photoparoxysmal Response 2

For a phenotypic description and a discussion of genetic heterogeneity of photoparoxysmal response, see PPR1 (132100).

Mapping

By linkage analysis of 25 families in which at least 2 sibs were affected with either PPR or traits of idiopathic generalized epilepsy (IGE; see 600669), Tauer et al. (2005) identified a putative disease locus on chromosome 13q31.3 (MOD score of 3.64 at marker D13S1230 under a recessive mode of inheritance). Of 121 family members, 68 displayed PPR and 69 had IGE or unprovoked generalized spike-wave discharges on EEG. Fifty-eight (84%) of the 69 individuals with IGE also showed PPR. The MOD score increased to a maximum of 4.83 when using additional trait definitions more specific for IGE traits, suggesting that the locus on 13q31 is related to IGE and may represent a gene involved in a common epileptogenic pathway shared by both PPR and IGE.