Balanced translocation in a patient with severe myoclonic epilepsy of infancy disrupts the sodium channel gene SCN1A.

In a patient with severe myoclonic epilepsy of infancy (SMEI), we identified a de novo balanced translocation, t(2;5)(q24.3,q34). The breakpoint on chromosome 2q24.3 truncated the SCN1A gene and the 5q34 breakpoint was within a highly conserved genomic region. Point mutations or microdeletions of SCN1A have previously been identified in SMEI patients, but this is the first report of a balanced translocation disrupting the SCN1A gene in an epilepsy patient. We therefore recommend that SMEI patients without SCN1A microdeletions or point mutations should be investigated for chromosomal rearrangements.