Idiopathic epilepsies with seizures precipitated by fever and SCN1A abnormalities

Epilepsia. 2007 Sep;48(9):1678-1685. doi: 10.1111/j.1528-1167.2007.01122.x. Epub 2007 Jun 11.

Abstract

Purpose: SCN1A is the most clinically relevant epilepsy gene, most mutations lead to severe myoclonic epilepsy of infancy (SMEI) and generalized epilepsy with febrile seizures plus (GEFS+). We studied 132 patients with epilepsy syndromes with seizures precipitated by fever, and performed phenotype-genotype correlations with SCN1A alterations.

Methods: We included patients with SMEI including borderline SMEI (SMEB), GEFS+, febrile seizures (FS), or other seizure types precipitated by fever. We performed a clinical and genetic study focusing on SCN1A, using dHPLC, gene sequencing, and MLPA to detect genomic deletions/duplications on SMEI/SMEB patients.

Results: We classified patients as: SMEI/SMEB = 55; GEFS+= 26; and other phenotypes = 51. SCN1A analysis by dHPLC/sequencing revealed 40 mutations in 37 SMEI/SMEB (67%) and 3 GEFS+ (11.5%) probands. MLPA showed genomic deletions in 2 of 18 SMEI/SMEB. Most mutations were de novo (82%). SMEB patients carrying mutations (8) were more likely to have missense mutations (62.5%), conversely SMEI patients (31) had more truncating, splice site or genomic alterations (64.5%). SMEI/SMEB with truncating, splice site or genomic alterations had a significantly earlier age of onset of FS compared to those with missense mutations and without mutations (p = 0.00007, ANOVA test). None of the remaining patients with seizures precipitated by fever carried SCN1A mutations.

Conclusion: We obtained a frequency of 71%SCN1A abnormalities in SMEI/SMEB and of 11.5% in GEFS+ probands. MLPA complements DNA sequencing of SCN1A increasing the mutation detection rate. SMEI/SMEB with truncating, splice site or genomic alterations had a significantly earlier age of onset of FS. This study confirms the high sensitivity of SCN1A for SMEI/SMEB phenotypes.

Publication types

  • Comparative Study

MeSH terms

  • Adolescent
  • Adult
  • Child
  • Child, Preschool
  • Chromatography, High Pressure Liquid / methods
  • Chromosome Mapping / methods
  • DNA Mutational Analysis
  • Epilepsies, Myoclonic / genetics*
  • Epilepsy, Generalized / genetics*
  • Female
  • Fever / complications
  • Genotype
  • Humans
  • Infant
  • Male
  • Mutation / genetics*
  • NAV1.1 Voltage-Gated Sodium Channel
  • Nerve Tissue Proteins / genetics*
  • Phenotype
  • RNA Splicing / genetics
  • Seizures, Febrile / genetics*
  • Sodium Channels / genetics*
  • Syndrome

Substances

  • NAV1.1 Voltage-Gated Sodium Channel
  • Nerve Tissue Proteins
  • SCN1A protein, human
  • Sodium Channels