Genetic linkage analyses have identified a number of loci for familial FS, including the loci on chromosome 19p13.3, 2q23-q24, 5q14-q15 and 18p11.2 containing the genes encoding casein kinase I gamma 2 isoform (CSNK1G2; 19p13.3), sodium channel, voltage-gated, type I, alpha subunit (SCN1A; 2q24.3), G protein-coupled receptor 98 (GPR98; 5q13) and inositol(myo)-1(or 4)-monophosphatase 2 (IMPA2; 18p11.2), respectively [61-64]. Here, SCN1A is linked to Feingold syndrome.