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We recently reported mutations in the sodium channel gene SCN2A in two families with benign familial neonatal-infantile seizures (BFNISs). Here, we aimed to refine the molecular-clinical correlation of SCN2A mutations in early childhood epilepsies. SCN2A was analyzed in 2 families with probable BFNIS, 9 with possible BFNIS, 10 with benign familial infantile seizures, and in 93 additional families with various early childhood epilepsies. Mutations effecting changes in conserved amino acids were found in two of two probable BFNIS families, in four of nine possible BFNIS families, and in none of the others. Our eight families had six different SCN2A mutations; one mutation (R1319Q) occurred in three families. BFNIS is an autosomal dominant disorder presenting between day 2 and 7 months (mean, 11.2 +/- 9.2 weeks) with afebrile secondarily generalized partial seizures; neonatal seizures were not seen in all families. The frequency of seizures varied; some individuals had only a few attacks without treatment and others had clusters of many per day. Febrile seizures were rare. All cases remitted by 12 months. Ictal recordings in four subjects showed onset in the posterior quadrants. SCN2A mutations appear specific for BFNIS; the disorder can now be strongly suspected clinically and the families can be given an excellent prognosis.

Author(s): Valente, E M; Brancat, F; Silhavy, J L; Castori, M; March, S E; Barrano, G; Bertini, E; Boltshauser, E; Zaki, M S; Abdel-Aleem, A; Abdel-Salam, GMH; Bellacchlo, E; Battini, R; Cruse, R P; Dobyns, W B; Krishnamoorthy, K S; Lagier-Tourenne, C; Magee, A; Pascual-Castroviejo, I; Salpietro, C D; Sarco, D; Dallapiccola, B; Gleeson, J G | Abstract: Joubert syndrome (JS) is a recessively inherited developmental brain disorder with several identified causative chromosomal loci. It is characterized by hypoplasia of the cerebellar vermis and a particular midbrain-hindbrain "molar tooth" sign, a finding shared by a group of Joubert syndrome-related disorders (JSRDs), with wide phenotypic variability. The frequency of mutations in the first positionally cloned gene, AHI1, is unknown. Methods: We searched for mutations in the AHI1 gene among a cohort of 137 families with JSRD and radiographically proven molar tooth sign. Results: We identified 15 deleterious mutations in 10 families with pure JS or JS plus retinal and/or additional central nervous system abnormalities. Mutations among families with JSRD including kidney or liver involvement were not detected. Transheterozygous mutations were identified in the majority of those without history of consanguinity. Most mutations were truncating or splicing errors, with only one missense mutation in the highly conserved WD40 repeat domain that led to disease of similar severity. Interpretation AHI1 mutations are a frequent cause of disease in patients with specific forms of JSRD.